phil took 1/5 of a piece of cheese and rena took 4/9 of the remaining amount?
If you want to know what fraction of the cheese is left >>
1/5 = 9/45
4/9 = 20/45
9/45 + 20/45 = 29/45
45/45 - 29/45 = 16/45
1/5 = 9/45
4/9 = 20/45
9/45 + 20/45 = 29/45
45/45 - 29/45 = 16/45