Question 820393
(3,-1)
(7,-8)
y=mx+b
-1=3m+b
-1-3m=b

-8=7m+b
-8-7m=b
-1-3m=b
so
-8-7m=-1-3m
-7=4m
-7/4=m
b = 17/4,   m = -7/4
y=-7/4x+17/4 slope intercept form
or 
4y=-7x+17

solve for what unknown?