You can solve this by substitution. Since the first equation is y=4x, you can put a 4x where you see a y in the second equation.
-3x-6(4x)=27
-3x-24x=27 (distribute)
-27x=27 (combine like terms)
x=-1 (divide both sides by -27)
So we know the answer must be A
Hope this helps!
