# Eliminating a variable

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

Quiz:

# Intro quiz - Recap from previous lesson

Before we start this lesson, let’s see what you can remember from this topic. Here’s a quick quiz!

Q1.If x=3 and 2x+5y=41, what is the value of y?

1/5

Q2.7x+2y=24 AND 4x+2y=18. Find the value of 3x

2/5

Q3.7x+2y=24 AND 4x + 2y = 18. Find the value of y

3/5

Q4.9x +6y=168 AND 9x +4y=160. Solve

4/5

Q5.4x +8y=116 AND 4x +4y=68. Solve

5/5

Quiz:

# Intro quiz - Recap from previous lesson

Before we start this lesson, let’s see what you can remember from this topic. Here’s a quick quiz!

Q1.If x=3 and 2x+5y=41, what is the value of y?

1/5

Q2.7x+2y=24 AND 4x+2y=18. Find the value of 3x

2/5

Q3.7x+2y=24 AND 4x + 2y = 18. Find the value of y

3/5

Q4.9x +6y=168 AND 9x +4y=160. Solve

4/5

Q5.4x +8y=116 AND 4x +4y=68. Solve

5/5

# Video

Click on the play button to start the video. If your teacher asks you to pause the video and look at the worksheet you should:

• Click "Close Video"
• Click "Next" to view the activity

Your video will re-appear on the next page, and will stay paused in the right place.

# Worksheet

These slides will take you through some tasks for the lesson. If you need to re-play the video, click the ‘Resume Video’ icon. If you are asked to add answers to the slides, first download or print out the worksheet. Once you have finished all the tasks, click ‘Next’ below.

Quiz:

# Eliminating a variable: add or subtract?

Don’t worry if you get a question wrong! Forgetting is an important step in learning. We will recap next lesson.

Q1.3x+2y=5 AND 3x-2y=7. If I add these two equations together, which unknown will be eliminated?

1/5

Q2.3x+2y=5 AND 3x-2y=7. If I subtract the two equations, which unknown will be eliminated?

2/5

Q3.3x-5y=17 AND 2x-5y=10. Subtract the first equation from the second equation.

3/5

Q4.2x-5y=10 AND 3x-5y=17. Add the two equations together.

4/5

Q5.3x-5y=17 AND 7x-5y=20. How can I eliminate y from these simultaneous equations?

5/5

Quiz:

# Eliminating a variable: add or subtract?

Don’t worry if you get a question wrong! Forgetting is an important step in learning. We will recap next lesson.

Q1.3x+2y=5 AND 3x-2y=7. If I add these two equations together, which unknown will be eliminated?

1/5

Q2.3x+2y=5 AND 3x-2y=7. If I subtract the two equations, which unknown will be eliminated?

2/5

Q3.3x-5y=17 AND 2x-5y=10. Subtract the first equation from the second equation.

3/5

Q4.2x-5y=10 AND 3x-5y=17. Add the two equations together.

4/5

Q5.3x-5y=17 AND 7x-5y=20. How can I eliminate y from these simultaneous equations?

5/5

# Lesson summary: Eliminating a variable

## Time to move!

Did you know that exercise helps your concentration and ability to learn?

For 5 mins...

Move around:
Walk

On the spot:
Chair yoga