3x+ay-13=0
x+ay-2=0
2x-11=0
x=11/2
x-2y+5=0
y=(x+5)/2=21/4
2x+y-5b=0
11+21/4=5b
65/4=5b
b=13/4
11/2+21a/4=2
a=-2/3