Ok so I totally forgot how to find a common denominator when your adding fractions, could someone please tell me the steps to do that? :)

multiply.

Multiply the denominators together and this gives the new denominator.
Divide each denominator into the new dominator and multiply by the numerator.

3/7+5/8

new denominator is 7*8 = 56

so addition is now

(3*8)+(5*7)
___________

7*8