17/80 is in its simplest form.
80/340 = 4/17
34/80 = 17/40
17/20
10/17
68/80 = 34/40 = 17/20 <-----------------------------
21/80 is already in its simplest form
9/80 is in its simplest form.
17 is prime and can't be reduced. If that's 80/17, it is in its simplest form. You could also call it 4 and 12/17.
36/80 in simplest form is 9 over 20
It already is in simplest form.
27 over 80!
30/80 would be 3/8 in simplest form.