11/13 is already in its simplest form
11 over 13 is in simplest form because they are both prime numbers and cant be divided by anything.
11 over 13
33/39 in simplest form is 11/13.
11/13
11/13
11/13
11/13
77/91 = 11/13
11/13
Since there is a common factor of 7, this becomes 11 over 13 (that is, 11/13)
4/13 is in its simplest form.