to solve this you must first find a least common multiple... AKA same denominator
5/8 and 3/4 can both have a denominator of 16 (8*2 & 4*4)
now multiply 5 by 2 (10) so that the fraction is now 10/16
do the same thing with the other fraction so that the fraction looks like this...
12/16
12/16 > 10/16
because 12 is greater than 10