12 Math Questions

The only questions that I need to have completed are numbers 3, 8, 9, 11, 12, 13, 14, 15, 16, 18, 20 and 21.  11, 12 and 13 will be typed in.  For 11, show as much work as possible.  For 12, assume it goes through (0,-3).  For 13, assume it goes through (0,-1).  Those are the only ones that will be typed out and the rest are just going to be put in as multiple choice (a, b, c and d).