Please help with a and b.
IF THIS WILL HELP YOU TRY ON https://www.geogebra.org/calculator
'a' slope = (y1-y2)/ (x1-x2) = (8-17)/(4-8) = -9/-4 = 9/4
parallel slope, m is the same = 9/4
New line thru -12,20
(y-20) = 9/4 (x+12)
+37159 
