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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?

What does x = in this equation x+3+2x=x+5

Ten times the square of a non-zero number is eqaul to ninety times the number