Divide the numerator and the denominator by their greatest common factor. In this case, that is 20.
1/20
2/5
The lowest terms of the fraction 16 over 20 are 4/5 or 0.8
20 over 35 as a fraction in lowest terms is 4/7
25
20 over 96 reduced to its lowest term is 5/24
5/9
28
81/20 is already in lowest terms.
3/20
1/50
5/8