The smart way to improve grades

Comprehensive & curriculum aligned

Affordable pricing from £10/month

Substitute Numbers for Letters into an Expression

In this worksheet, students must substitute numbers in place of letters to evaluate the given expressions.

'Substitute Numbers for Letters into an Expression' worksheet

Key stage:  KS 3

Curriculum topic:  Algebra

Curriculum subtopic:  Substitute Numerical Values for Formulae/Expressions

Difficulty level:  

Worksheet Overview

QUESTION 1 of 10

In algebra, we use a letter to represent an unknown number. 

Sometimes we want to substitute a number for the letter in an expression.

 

Example 1

Evaluate 2a - b when a = 6 and b = 7.

 

Answer 1

2a - b means (2 × a) - b 

So this is (2 × 6) - 7

i.e.  12 - 7 = 5.

 

 

Example 2

Work out the value of 5(x - 2) when x = 9.

 

Answer 2

Substitute x for 9 to get

5(9 - 2) which means 5 × (9 - 2).

Now work out the brackets first to get 9 - 2 = 7.

So this is 5 × 7 = 35

Work out the value of

 

2x + y   when  x = 6 and  y = 7

 

Work out the value of

 

2x + y   when  x = 5 and  y = 4

Evaluate

 

2x + y   when  x = 10 and  y = 9

Evaluate

 

2x - y   when  x = 10 and  y = 9

Evaluate

 

2(x - 5)   when  x = 10

Evaluate

 

12(x - 6)    when  x = 9

 

Evaluate

 

9(x + 6)   when  x = 5

Evaluate

 

2(x + y)   when  x = 10 and  y = 9

Evaluate

 

2(x + y)   when  x = 1 and  y = 19

Work out the value of 

 

5x - y    when  x = 2 and  y = 10

  • Question 1

Work out the value of

 

2x + y   when  x = 6 and  y = 7

 

CORRECT ANSWER
19
EDDIE SAYS

Step 1: Rewrite the expression with the hidden multiply signs

2 x X + y

Step 2: Substitute in the numbers you are given

2 x 6 + 7

Step 3: Evaluate the expression (don't forget to use BODMAS)

12 + 7 = 19

  • Question 2

Work out the value of

 

2x + y   when  x = 5 and  y = 4

CORRECT ANSWER
14
EDDIE SAYS

Step 1: Rewrite the expression with the hidden multiply signs

2 x X + y

Step 2: Substitute in the numbers you are given

2 x 5 + 4

Step 3: Evaluate the expression (don't forget to use BODMAS)

10 + 4 = 14

  • Question 3

Evaluate

 

2x + y   when  x = 10 and  y = 9

CORRECT ANSWER
29
EDDIE SAYS

Step 1: Rewrite the expression with the hidden multiply signs

2 x X + y

Step 2: Substitute in the numbers you are given

2 x 10 + 9

Step 3: Evaluate the expression (don't forget to use BODMAS)

20 + 9 = 29

  • Question 4

Evaluate

 

2x - y   when  x = 10 and  y = 9

CORRECT ANSWER
11
EDDIE SAYS

Step 1: Rewrite the expression with the hidden multiply signs

2 x X - y

Step 2: Substitute in the numbers you are given

2 x 10 - 9

Step 3: Evaluate the expression (don't forget to use BODMAS)

20 - 9 = 11

  • Question 5

Evaluate

 

2(x - 5)   when  x = 10

CORRECT ANSWER
10
EDDIE SAYS

 

Step 1: Substitute in the numbers you are given

2(10 - 5)

Step 2: Evaluate the expression (don't forget to use BODMAS)

2 x 5 = 10

  • Question 6

Evaluate

 

12(x - 6)    when  x = 9

 

CORRECT ANSWER
36
EDDIE SAYS

Step 1: Substitute in the numbers you are given

12(9 - 6)

Step 2: Evaluate the expression (don't forget to use BODMAS)

12 x 3 = 36

  • Question 7

Evaluate

 

9(x + 6)   when  x = 5

CORRECT ANSWER
99
EDDIE SAYS

Step 1: Substitute in the numbers you are given

9(5 + 6)

Step 2: Evaluate the expression (don't forget to use BODMAS)

9 x 11 = 99

  • Question 8

Evaluate

 

2(x + y)   when  x = 10 and  y = 9

CORRECT ANSWER
38
EDDIE SAYS

Step 1: Substitute in the numbers you are given

2(10 + 9)

Step 2: Evaluate the expression (don't forget to use BODMAS)

2 x 19 = 38

  • Question 9

Evaluate

 

2(x + y)   when  x = 1 and  y = 19

CORRECT ANSWER
40
EDDIE SAYS

Step 1: Substitute in the numbers you are given

2(1 + 19)

Step 2: Evaluate the expression (don't forget to use BODMAS)

2 x 20 = 40

  • Question 10

Work out the value of 

 

5x - y    when  x = 2 and  y = 10

CORRECT ANSWER
0
EDDIE SAYS

Step 1: Rewrite the expression with the hidden multiply signs

5 x X - y

Step 2: Substitute in the numbers you are given

5 x 2 - 10

Step 3: Evaluate the expression (don't forget to use BODMAS)

10 - 10 = 0

---- OR ----

Sign up for a £1 trial so you can track and measure your child's progress on this activity.

What is EdPlace?

We're your National Curriculum aligned online education content provider helping each child succeed in English, maths and science from year 1 to GCSE. With an EdPlace account you’ll be able to track and measure progress, helping each child achieve their best. We build confidence and attainment by personalising each child’s learning at a level that suits them.

Get started
laptop

Start your £1 trial today.
Subscribe from £10/month.