  # Use Substitution in Simple Algebraic Expressions

In this worksheet, students will substitute numbers for letters and work out the value of simple expressions with two variables. Key stage:  KS 3

Curriculum topic:   Algebra

Curriculum subtopic:   Substitute Numerical Values for Formulae/Expressions

Difficulty level:   #### Worksheet Overview

When we substitute a number for a letter, we simply replace the letter with the number.

However, we must remember that 4b means 4 x b.

Example

Work out the value of the following expression when a = 4 and b = -5

3a - 7 - 2b

3a - 7- 2b

= (3 x a) - 7 - (2 x b)

= (3 x 4) - 7 - (2 x - 5)

= 12 - 7 - -10

= 12 - 7 + 10

15

Did you remember the rules for negative numbers?

One negative and one positive makes a negative.

Two positives or two negatives makes a positive.

These facts will be very important in this activity!! ### What is EdPlace?

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