Explanation:
6. remove 3 from 83, you will have 80 and then divide by 4 = 20 students in a class.
7. Subtract 8.80 from 24.80, you will get 16 dollars. Do 16 ÷ 5 = 3.2 as the cost of each pencil.
9. 94- 6 = 88 so, 88 ÷ 4 = 22.
10. 13.40 -7.60 = 5.8 as his weekly allowance.
I hope it helps.