Question 1153976
The two equations you have given are

x = 3 - 3y ---- (1)
x + 3y = -6 ---- (2)

Moving x and y terms to same side in (1) we get
x + 3y = 3
and from (2) we see x + 3y = -6

Clearly 3 is NOT equal to -6. So there is something wrong with one of the equations and they cannot be solved as such. Please check and resubmit your problem.