36/80 in simplest form is 9 over 20
4/80 = 1/20 or 5% or .05 in it's simplest form.1/20
76/80 = 19/20
9/20
7/20
3/20
17/20
20/21
68/80 = 34/40 = 17/20 <-----------------------------
The answer is 4/5. To get this you divide 80 by 20 and 100 by 20.
28/80 = 7/20
21/80 is already in its simplest form