Hi again!
2x - y = 80
5y = x
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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
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