Answer:
-7
Explanation:
y - x = 9
10 + 2x = -2y
Solve for y in the first equation.
y = 9 + x
Put y as 9 + x in the second equation and solve for x.
10 + 2x = -2(9 + x)
10 + 2x = -18 - 2x
2x + 2x = -18 - 10
4x = -28
x = -28/4
x = -7
y−x=9 ⇒ y=x+9
10+2x=−2y
5+x= -y ====== replacing y with x+9
5+x= -x-9
2x= -14
x= -7
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