Question

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.
The system of equations shown can be used to find the number of multiple-choice questions, m, and the number of free-response questions, f, on the test.

m + f = 15

3m + 5f = 51

How many multiple-choice questions are on the test?

Answer 1

M + f = 15....multiply by -5
3m + 5f = 51
-----------------
-5m - 5f = - 75 (result of multiplying by -5)
3m + 5f = 51
----------------add
-2m = - 24
m = -24/-2
m = 12 <=== 12 multiple choice questions

Answer 2

Answer:

c

Step-by-step explanation: