solve by the subtraction method

5x+6y=0
x=34-8y

5 x + 6 y = 0

1 x + 8 y = 34 multiply all terms by 5

5 x + 6 y = 0
5 x + 40 y = 170
-----------------
0 x - 34 y = -170

y = 5
x = -6