Explain how to divide an amount by 3

Students are given 3 minutes for each multiple-choice question and 5 minutes for each free-response question on a test. there are 15 questions on the test, and students are given 51 minutes to take it.how many multiple-choice questions are on the test?

At a sale this week, a desk is being sold for $213. this is a 29% discount from the original price. what is the original price?

Does the point (1, sqrt 7) lie on circle shown.