For this, you have to do 2 1/4 - 1 2/5. First, you have to find a common denominator, so the common denominator for these fractions is 20. 4 can go into 20 five times so the numerator is 5. 5 can go into 20 4 times, so you have to do 2 x 4, so it's 8. Now the equation is 2 5/20 - 1 8/20. You cannot subtract 5 - 8, so you take 1 from 2 and add 20 to the numerator, so now it's 1 25/20 - 1 8/20. The answer is now 17/20. :)