Question

How do u substitute?

Answer 1

Hi again!

2x - y = 80
5y = x

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Ok stop talking and let's get to work!

We need to solve 2x - y = 80 for y

2x - y = 80

-y = 80 - 2x

Multiply both sides by -1 because y cannot be negative

-y * -1 = -1(80 - 2x)

y = 2x - 80

Now we can substitute 2x - 80 for y in 5y = x

5y = x

5(2x - 80) = x

Use the distributive property

(5)(2x) + (5)(-80) = x

10x - 400 = x

Add -x on both sides

10x - 400 - x = x - x

9x - 400 = 0

Add 400 on both sides

9x - 400 + 400 = 0 + 400

9x = 400

Divide both sides by 9

9x/9 = 400/9

x = 400/9

To find y, we can substitute 400/9 for x in y = 2x - 80

y = 2x - 80

y = 2(400/9) - 80

y = 800/9 - 80

y = 800/9 - 80/1

y = 800/9 + -720/9

y = (800 - 720)/9

y = 80/9

Thus,

The answers are: y = 80/9 and x = 400/9

As always, it is my pleasure to help students like you