i need help with a word problem

Question

This is the word problem

 

There are 912 yellow chairs and blue chairs altogether in an auditorium.the blue chair are arranged in 36 rows with 12 chairs in each row. The are arranged in rows of 20.how many rows of yellow chairs are there

 

Answer 1

blue:36*12=432

912-432=480 yellow chairs

480/20=24 rows of yellow chairs