Nine over 21 in its simplest form is 3/7
Common factor is seven. So it is 3 over nine
21/80 is already in its simplest form
21/5 is the simplest form.
440/21 is in its simplest form.
21/10 is in its simplest form.
10/21 is in its simplest form.
4/21 is in its simplest form.
21/16 is in its simplest form.
21/52 is the simplest form.
21/100 is in its simplest form.
21/46 is the simplest form.
21/22 is in simplest form.