I need help with this

Question

If the recipe calls for 5 3/7 cups of flour. You already put in 2 1/2. How many more cups do you need to put in.

Answer 1

common denominator first:

(5 + 3/7) - (2 + 1/2) = (5 + 6/14) - (2 + 7/14) = (4 + 20/14) - (2 + 7/14) = 2 + 13/14

impropers first, then common denominator:

38/7 + 5/2 = 76/14 - 35/14 = 41/14 = 2 + 13/14