Question

is 300 student can sit in 12 class room how many rooms need to be added similarly for 375 students​

Answer 1

15 class rooms
300 divided by 12 is 25, so if there is 12 class rooms for 300 and you need 75, 25*3 is 75
12+3 is 15:)

Answer 2

15 rooms will be needed in order for 375 students to fit.