20, 22, 31 and 32. I have the answers, I just wanted to see adifferent way of working them out.

2 / 20.- 175 х 1,5 y + 5 12 2 2x у X y -+-+ 5 6 16 15 3 1 22.- NI y I + х 1 + - 31.- bx + ay - 2ab bx - y = 0 32.- ax = by 7 bx + ay = abc