Use each pair of points given below to write a system of equations in $y=mx+b$ form to find the equation of a line that passes through the points.  

1. $(20,2)$ and $(32,−4)$ 

   Step 1(a):

   $20=m(2)+b$

   Step 2(a):

   $32=m(−4)+b$

2. $(−3,−17)$ and $(12,−7)$ 

   Hint (b):

   Refer to part (a).