Find a common denominator
the CD is 15 because 3 and 5 both go into them.
find how many time the bottom part of the first fraction can go into there.
in this case, 3 can go into 15, 5 times
so then youll mutiple your top number by 5
repeat this for the next fraction
Once you have your four fractions, subtract the top of the two new fractions
in this case it'll be 10 and 12
then put that over 15