12=k*(-2)+b
-16=k*(-8)+b
12=-2k+b
-16=-8k+b
b=12+2k
-8k+b=-16
-8k+12+2k=-16
-6k=-28
k=14/3
b=12+2*14/3
b=12+28/3
b=36/3+28/3
b=64/3