Your denominator is going to be 4 digits. "18,18,18,18".
I think you just have to add all of the totals up??
42 divided by 6 is 7. if you subtract 4 from 7 the answer would be 3
7 goes into 63 9 times so 6/7 you would take away one 9 so it would be 6 times 9 which is equal to 54
Answer: 54 students