Question

HHow many pupils are there in a class if two pupils remain after four rows of seats are filled, and nine pupils remain after three rows of seats are filled?

a. 21
b. 22
c. 28
d. 30
e. 32

please answer and explain

Answer 1

If there are 9 left over from 3 rows and 2 left over from 4 rows, each row must seat 9-2 = 7 pupils

So, 7*4 +2 = ?

Or, 7*3 +9 = ?