Well the fraction means 15 out of 20. Each can be divided by 5, so if you divide 15 by 5, you get 3. If you divide 20 by 5, you get 4. 15/20 would equal 3/4 BECAUSE 20 is the total amount, and there are 4 fives. with 15, there are 3 fives. If this is confusing I can explain a different way.
