They give you an "x =" statement so you plug in the right side of the equals sign into the first equation wherever x appears. So...
y = 10 - 2(y - 4)
y = 10 - 2y + 8
y = 18 - 2y
y + 2y = 18
3y = 18
y = 6
Now we plug in this result for the y-value into the "x =" statement.
x = 6 - 4
x = 2
Your answer is (2, 6)
