Answer:
x = - 7
Step-by-step explanation:
Given the 2 equations
y - x = 9 → (1)
10 + 2x = - 2y → (2)
Rearrange (1) expressing x in terms of y by adding x to both sides
y = x + 9
Substitute y = x + 9 into (2)
10 + 2x = - 2(x + 9) ← distribute
10 + 2x = - 2x - 18 ( add 2x to both sides )
10 + 4x = - 18 ( subtract 10 from both sides )
4x = - 28 ( divide both sides by 4 )
x = - 7
