so you have to get the fractions with the same denominator (the number on the bottom)
the easiest way to do it is just multiply each with the opposing denominator
EXAMPLE: For 3/8 you multiply top and bottom by 5, the other fraction's denominator and you would get 15/40
then for 2/5 you multiply it by 8 and get 16/40
ANSWER: 6 15/40 + 7 16/40 = 13 31/40