What is 3 1/2 t 1 1/3

and 4 5/7 t 3 3/4

3 and 1/2 + 1 and 1/3 = 4 and 5/6

4 and 5/7 + 3 and 3/4 = 8 and 13/28

Change the denominators so that they are the same. Whatever you do to the bottom, do to the top.

Or you could change them into improper fractions.