Ok so set it up like this 36/90. We want to find the greatest common factor of both numbers! So 36 and 90 both share 6. So we divide the numerator(top) and the denominator (bottom) by 6. On top we get a quotient of 6 and on the bottom we get 15. We are still not done yet! 6 and 15 can be broken down even more. Ask yourself what do they share in common. The answer is 3! So divide both the top and bottom by 3 and you get 3/5. Hoped that helped you out!!