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Substitute Numbers for Letters in an Expression

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

'Substitute Numbers for Letters in an Expression' worksheet

Key stage:  KS 3

Year:  Year 7 Maths worksheets

Curriculum topic:   Algebra

Curriculum subtopic:   Substitute Numerical Values for Formulae/Expressions

Popular topics:   Algebra worksheets, Year 7 Algebra worksheets

Difficulty level:  

Worksheet Overview

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

Sometimes we need 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

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).


Multiply everything inside the bracket with everything outside the bracket!


5 x 9 = 45

5 x -2 = -10

45 - 10 = 35


Algebra can look complicated but it will soon become second-nature to you.


The important thing is to take it one step at a time and write down all the stages.


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