Solve the word problem please.

Question

A test has 25 questions and is worth a total of 100 points. It consists of multiple-choice that are worth 8 points each and short answer questions that are worth 3 points each. How many multiple choice questions are on the test? 

Answer 1

M+S = 25

8M+3S =100

8M + 3(25-M) = 100

8M -3M = 100-75

5M = 25

M = 5 multiple choice questions

S= 25-5 = 20 short answer questions