Can someone please explain on how to do this? I’m really confused

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?

Interpret the following expression (5y^2-7)^3/(2y)^2

What line represents the relationship between r and s