  # Solve Simple Simultaneous Equations

In this worksheet, students will solve simple simultaneous equations by eliminating one variable. Key stage:  KS 3

Curriculum topic:   Algebra

Curriculum subtopic:   Understand Expressions, Equations, Inequalities, Terms and Factors

Difficulty level:   #### Worksheet Overview

Simultaneous equations involve two variables, the values of which need to be found.

The following method quickly eliminates one of the variables, so that the resulting equation can be solved normally.

Example 1

Solve simultaneously:

x + y = 4

x - y = 2

x + y = 4     (a)

x - y = 2      (b)

We can eliminate y by adding (a) to (b)

This gives 2x = 6

So x = 3

Substitute this x value into one of the equations, say (a) to get

3 + y = 4

y = 1

Check by putting this into the other equation (b) to get 3 - 1 = 2

Solution is x = 3, y = 1

Example 2

Solve simultaneously:

3x + y = 25

x + y = 11

3x + y = 25     (a)

x + y = 11      (b)

We can eliminate y by subtracting (b) from (a) to get

2x = 14

x = 7

Substitute this x value into say equation (b) to get 7 + y = 11

So y = 4

Check in equation (a) to get 3 x 7 + 4 = 21 + 4 = 25

Solution is x = 7, y = 4

These may look tricky but the key is to take them slowly, one step at a time - and write everything down!

### 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 