Substitution Worked Solutions — GCSE Maths

Fully worked, step-by-step solutions to GCSE Substitution questions. See exactly how to solve problems on substitution, multiplication, addition, order of operations.

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GCSE Foundation70 questionsStep-by-step solutions
Question 1
1 markeasy
Work out the value of 3x3x when x=4x = 4.

Worked solution

  1. Write down the expression

    3x3x

    You need the value of 3x, which means 3 multiplied by x.

  2. Substitute x=4x = 4

    3×43 \times 4

    Replace the letter x with the number 4.

  3. Work out the answer

    3×4=123 \times 4 = 12

    Three lots of four is twelve.

Answer
1212
Question 2
1 markeasy
Work out the value of x+7x + 7 when x=5x = 5.

Worked solution

  1. Write down the expression

    x+7x + 7

    You need the value of x add 7.

  2. Substitute x=5x = 5

    5+75 + 7

    Replace x with 5.

  3. Work out the answer

    5+7=125 + 7 = 12

    Five add seven is twelve.

Answer
1212
Question 3
1 markeasy
Work out the value of 2a+12a + 1 when a=6a = 6.

Worked solution

  1. Write down the expression

    2a+12a + 1

    2a means 2 multiplied by a.

  2. Substitute a=6a = 6

    2×6+12 \times 6 + 1

    Replace a with 6.

  3. Work out the answer

    12+1=1312 + 1 = 13

    Do the multiplication first: 2×6=122 \times 6 = 12, then add 11.

Answer
1313
Question 4
1 markeasy
Work out the value of 10−y10 - y when y=3y = 3.

Worked solution

  1. Write down the expression

    10−y10 - y

    You need 10 subtract y.

  2. Substitute y=3y = 3

    10−310 - 3

    Replace y with 3.

  3. Work out the answer

    10−3=710 - 3 = 7

    Ten subtract three is seven.

Answer
77
Question 5
1 markeasy
Work out the value of x2\frac{x}{2} when x=8x = 8.

Worked solution

  1. Write down the expression

    x2\frac{x}{2}

    This means x divided by 2.

  2. Substitute x=8x = 8

    82\frac{8}{2}

    Replace x with 8.

  3. Work out the answer

    82=4\frac{8}{2} = 4

    Eight divided by two is four.

Answer
44

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