Question

20X=28-8Y

-8X=-56-8Y

Answer 1

20x = 28 - 8y ------equation 1
-8x = -56 - 8y -----equation 2
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To eliminate y,
Subtract equation 2 from equation 1
20x = 28 - 8y
- -8x =-56 - 8y
28x = 84
Divide the whole equation with 28
28y/28 = 84/28
x = 3
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Substitute x=3 to either of the two equations above
In this case, let's use equation 1
20x = 28 - 8y
20(3) = 28 - 8y
60 = 28 - 8y
60 - 28 = -8y
32 = -8y
Divide the whole equation with -8
-4 = y
y = -4