15/28 is the simplest form and, by definition, the simplest form must be equivalent to other forms of the ratio.
6/45 = 2/15
71/15 is in its simplest form.
8:15 is already in simplest form.
15 to 1
15/7 is in its simplest form.
10 to 15 in its simplest form is 2 to 3
8/15 is in its simplest form.
15/16 is in its simplest form.
8/15 is in its simplest form.
15/29 is the simplest form.
11/15 is the simplest form.