# Eliminating a variable

## Lesson details

### Key learning points

1. In this lesson, we will determine how to eliminate a variable by adding or subtracting one equation to or from the other.

### Licence

This content is made available by Oak National Academy Limited and its partners and licensed under Oak’s terms & conditions (Collection 1), except where otherwise stated.

## Video

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## Worksheet

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## Starter quiz

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### 5 Questions

Q1.
If x=3 and 2x+5y=41, what is the value of y?
3
5
7.8
Q2.
7x+2y=24 AND 4x+2y=18. Find the value of 3x
2
5
7
Q3.
7x+2y=24 AND 4x + 2y = 18. Find the value of y
2
6
7
Q4.
9x +6y=168 AND 9x +4y=160. Solve
Others
x=15 and y = 18
x=9 and y=6
y=16 and x=4
Q5.
4x +8y=116 AND 4x +4y=68. Solve
x=12 and y=5
x=4 and y = 8
x=8 and y = 4

## Exit quiz

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### 5 Questions

Q1.
3x+2y=5 AND 3x-2y=7. If I add these two equations together, which unknown will be eliminated?
both
neither
x
Q2.
3x+2y=5 AND 3x-2y=7. If I subtract the two equations, which unknown will be eliminated?
both
neither
y
Q3.
3x-5y=17 AND 2x-5y=10. Subtract the first equation from the second equation.
5x=27
x-10y=7
y=7
Q4.
2x-5y=10 AND 3x-5y=17. Add the two equations together.
10y=27