you need to change the mixed numbers 3 7/8 and 6 2/5 to improper fractions. do you multiply then add 3×8+7 and then you put that over 8 because that was the original denominator. do the same for the other then multiply across. the error was that they just multiplied 3 and 6 which is 18 and 7 and 2 which is 14 and 8 and 5 which is 40. they did not change to a improper fraction then multiply like you are supposed to
