In order to subtract mixed fractions, you'll need to look at the denominators carefully. If the denominators do not match, you'll need to find a common denominator. For example, 5 2/3 minus 3 4/5 do not have the same denominator. The lowest common denominator for them is 15. Next, you will need to determine what number you will need to multiply each fraction by in order to get like denominators. Subtract and simplify. Your answer should be 1 13/15. To multiply, you would need to convert them to improper fractions. 5 2/3 becomes 17/3. 3 4/5 becomes 19/5. 17/3 minus 19/5 equals 28/15. When you simplify, you get 1 13/15.