3 + y = x
y = -2x + 9
Substituting the first equation into the second equation, we get:
y = -2(3 + y) + 9
y = -2(3) - 2(y) + 9
y = -6 - 2y + 9
y + 2y = -6 + 9
3y = 3
y = 3/3
y = 1
Replacing this value into the first equation,
x = 3 + y
x = 3 + 1
x = 4