Answer:
68.44%
Explanation:
You compute the average the way you compute any average: add up the numbers and divide by their number.
Multiplication is a useful way to shorten the effort of repeated addition.
(64% × 3 + 58% × 7 + 88% × 3 +33% + 100% × 2)/(3 +7 +3 + 1 + 2)
= 1095%/16 = 68.4375%
≈ 68.44% . . . the average mark for the class