Write the equations in standard form to not get confused.
-x + 2y = 6........ 1.
x - 6y = -18....... 2.
add these equation, x will cancel out and you will be left with,
-4y = -12
y = 3
plug this value of y in either 1 or 2. lets plug it in 2,
x - 6(3) = -18
x = -18 + 18 = 0
∴x = 0
