17. I wouldn't have succeeded if my parents hadn't encouraged and supported me.
but for my parents's encouragement and support , I wouldn't have succeeded
18. If he didn't help me, my children wouldn't enter primary school. (without)
without his help , my children wouldn't enter primary school.
19. Peter left his job yesterday because of his low salary. (if)
if his salary  hadn't been low, Peter wouldn't have left his job yesterday