Answer: x = -6
Step-by-step explanation: The problem gave us the y value, so we can just substitute it into the equation and solve it.
y = x - 6
y = 2x
2x = x - 6 (substitute the y value into the equation)
1x = -6 (subtract x on each side)
x = -6 (1x is basically saying x so you do not need to divide)