The fraction 20/21 is already in lowest terms.
Since the numbers 20 and 21 share no common positive integer factors, 20/21 is expressed in its simplest form.
It is: 20/84 = 5/21 in its simplest form
21/20 is in its simplest form.
20/210 = 2/21
20/21
10/21
21/20
20/21
20/21
21/60 = 7/20
42/20 = 21/10 = 21/10
20/21 is in its simplest form.