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A17

Solve linear equations in one unknown algebraically (including those with the unknown on both sides of the equation); find approximate solutions using a graph

Linear equations

Worked answers, methods and verified real exam appearances for A17 on Edexcel GCSE Maths 1MA1.

Explanation

  • Keep an equation balanced by applying the same operation to both sides until the unknown is isolated. Expand brackets first, then collect unknown terms on one side and constants on the other.
  • With fractions, multiply every term by a common multiple of the denominators before simplifying.
  • A graphical solution is the xx-coordinate where graphs representing the two sides intersect, so its accuracy is limited by the graph scale.
  • The examiner awards method marks for valid algebraic steps; unexplained sign changes are not valid operations.
  • Check the solution by substituting it into the original equation and confirming both sides are equal.

Worked example

Solve 3(x2)4x+13=56\dfrac{3(x-2)}{4}-\dfrac{x+1}{3}=\dfrac56.

  1. 1.Multiply every term by 1212: 9(x2)4(x+1)=109(x-2)-4(x+1)=10.
  2. 2.Expand and collect terms: 9x184x4=109x-18-4x-4=10, so 5x=325x=32.
  3. 3.Divide by 55: x=325x=\dfrac{32}{5}.

Answer: x=325x=\dfrac{32}{5}.

Common mistakes

  • Don't multiply only the fractional terms, not every term, when clearing denominators.
  • Don't change the sign of a term when moving it without performing the same addition or subtraction on both sides.

Exam tip

For a multi-mark 'solve' question, keep each balancing step visible so an arithmetic slip does not lose the method marks.

Worked practice

Q1
Tier 1 · Easy

1

Solve 7x+5=337x+5=33.

(2)

(Total for Question 1 is 2 marks)

Mark scheme

Mark scheme for question 1
QuestionAnswerMarkMark scheme
1
  • x=4x=4
2Subtract 55 from both sides to get 7x=287x=28. Divide both sides by 77, giving x=4x=4.
Q2
Tier 2 · Standard

2

Draw y=4.5x2y=4.5x-2 and y=9.2xy=9.2-x on the same axes. Use the intersection to solve 4.5x2=9.2x4.5x-2=9.2-x, giving an estimate to one decimal place.

(4)

(Total for Question 2 is 4 marks)

Mark scheme

Mark scheme for question 2
QuestionAnswerMarkMark scheme
2
  • x2.0x\approx2.0
4The graphical solution is the xx-coordinate of the intersection. The lines meet at about (2.04,7.16)(2.04,7.16), so the requested estimate is x2.0x\approx2.0 to one decimal place.
Q3
Tier 3 · Hard

3

Solve 3x+15+132x7=5x+98\frac{3x+1}{5}+\frac{13-2x}{7}=\frac{5x+9}{8}.

(4)

(Total for Question 3 is 4 marks)

Mark scheme

Mark scheme for question 3
QuestionAnswerMarkMark scheme
3
  • x=3x=3
4Multiply every term by 280280: 56(3x+1)+40(132x)=35(5x+9)56(3x+1)+40(13-2x)=35(5x+9). Expanding gives 168x+56+52080x=175x+315168x+56+520-80x=175x+315, so 261=87x261=87x and x=3x=3.
Q4
Tier 1 · Easy

4

Solve 8x5=3x+308x-5=3x+30.

(2)

(Total for Question 4 is 2 marks)

Mark scheme

Mark scheme for question 4
QuestionAnswerMarkMark scheme
4
  • x=7x=7
2Subtract 3x3x from both sides to get 5x5=305x-5=30. Add 55 to both sides, so 5x=355x=35 and x=7x=7.
Q5
Tier 2 · Standard

5

Solve 0.6x1.7=0.2x+4.30.6x-1.7=0.2x+4.3.

(3)

(Total for Question 5 is 3 marks)

Mark scheme

Mark scheme for question 5
QuestionAnswerMarkMark scheme
5
  • x=15x=15
3Subtract 0.2x0.2x to obtain 0.4x1.7=4.30.4x-1.7=4.3. Add 1.71.7, giving 0.4x=60.4x=6. Dividing by 0.40.4 gives x=15x=15.
Q6
Tier 3 · Hard

6

Solve 52x34=x+735-\dfrac{2x-3}{4}=\dfrac{x+7}{3}.

(4)

(Total for Question 6 is 4 marks)

Mark scheme

Mark scheme for question 6
QuestionAnswerMarkMark scheme
6
  • x=4110x=\dfrac{41}{10}
4Multiply every term by 1212 to get 603(2x3)=4(x+7)60-3(2x-3)=4(x+7). Expanding gives 696x=4x+2869-6x=4x+28, so 41=10x41=10x and x=4110x=\dfrac{41}{10}.
Q7
Tier 2 · Standard

7

Solve 4(2x3)+5=3(x+6)4(2x-3)+5=3(x+6).

(3)

(Total for Question 7 is 3 marks)

Mark scheme

Mark scheme for question 7
QuestionAnswerMarkMark scheme
7
  • x=5x=5
3Expand both sides to get 8x12+5=3x+188x-12+5=3x+18. Therefore 8x7=3x+188x-7=3x+18, so 5x=255x=25 and x=5x=5.
Q8
Tier 3 · Hard

8

Solve 5x47=3x+811\dfrac{5x-4}{7}=\dfrac{3x+8}{11}.

(4)

(Total for Question 8 is 4 marks)

Mark scheme

Mark scheme for question 8
QuestionAnswerMarkMark scheme
8
  • x=5017x=\dfrac{50}{17}
4Cross-multiply to get 11(5x4)=7(3x+8)11(5x-4)=7(3x+8). Expanding gives 55x44=21x+5655x-44=21x+56, so 34x=10034x=100 and x=5017x=\dfrac{50}{17}. Substitution gives 26/1726/17 on each side.
Q9
Tier 3 · Hard

9

The value x=4x=-4 is the solution of 5(kx3)+7=2(kx+8)125(kx-3)+7=2(kx+8)-12. Work out kk and show the algebra leading to your answer.

(4)

(Total for Question 9 is 4 marks)

Mark scheme

Mark scheme for question 9
QuestionAnswerMarkMark scheme
9
  • k=1k=-1
4Substitute x=4x=-4: 5(4k3)+7=2(4k+8)125(-4k-3)+7=2(-4k+8)-12. This simplifies to 20k8=8k+4-20k-8=-8k+4, so 12k=12-12k=12 and k=1k=-1. Checking gives 1212 on both sides of the original equation.
Q10
Tier 3 · Hard

10

A student says that x=5x=5 solves 4(3x2)5=7x+224(3x-2)-5=7x+22. Show by substitution that this is incorrect. Solve the equation to find the correct value of xx.

(4)

(Total for Question 10 is 4 marks)

Mark scheme

Mark scheme for question 10
QuestionAnswerMarkMark scheme
10
  • At x=5x=5, the two sides are 4747 and 5757, so x=5x=5 is incorrect
  • x=7x=7
4When x=5x=5, the left side is 4(152)5=474(15-2)-5=47 and the right side is 35+22=5735+22=57, so the claim fails. Expanding the equation gives 12x13=7x+2212x-13=7x+22. Hence 5x=355x=35 and x=7x=7.

Verified exam appearances

SeriesPaperQuestionMarksCalculatorTierLinks
2023-111HQ75Non-calculatorHigherQPMS
2022-111FQ164Non-calculatorFoundationQPMS
2022-063FQ174AllowedFoundationQPMS
2024-113FQ63AllowedFoundationQPMS
2022-111FQ83Non-calculatorFoundationQPMS
2023-111FQ245Non-calculatorFoundationQPMS
2021-113FQ177AllowedFoundationQPMS
2023-112HQ43AllowedHigherQPMS
2023-113FQ162AllowedFoundationQPMS
2023-063FQ183AllowedFoundationQPMS
2021-111FQ164Non-calculatorFoundationQPMS
2022-112FQ147AllowedFoundationQPMS
2019-111FQ173Non-calculatorFoundationQPMS
2023-061FQ51Non-calculatorFoundationQPMS
2021-111FQ154Non-calculatorFoundationQPMS
2024-062HQ103AllowedHigherQPMS
2024-061FQ173Non-calculatorFoundationQPMS
2023-063FQ113AllowedFoundationQPMS
2019-061FQ104Non-calculatorFoundationQPMS
2019-063FQ154AllowedFoundationQPMS
2019-113HQ104AllowedHigherQPMS
2024-111FQ154Non-calculatorFoundationQPMS
2019-113FQ192AllowedFoundationQPMS
2023-112FQ253AllowedFoundationQPMS

Other points in A Algebra · graphs

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