2y=-x+9 (a)
3x-6y = -15 (b)
First, solve (a) for x:
2y=-x+9
x=9-2y
Replace x on (b) and solve for y:
3(9-2y) -6y=-15
27-6y-6y=-15
27-12y=-15
27+15 =12y
42 =12y
42/12= y
y= 3.5
Replace the value of y on any equation and solve for x:
x=9-2y
x = 9-2(3.5)
x= 9-7
x= 2