You are not giving enough information but in one of the calsses the average of student's height might be greater than the other class beacause one of the two classes needs to have 1 extra person than the other calss
Let x be that number:
x +10 -2 +4 + 3 - 1 - 7 +1 = 0
x +8 = 0
and x = - 8
Steps:
57.68÷8
=7.21minutes per hour
(p.s. make sure they don't want you to round!)
