need help solving this question

Question

A test is worth a total of 100 points. There are 19 questions on the test. Some questions are worth are worth 6 points and some are worth 4 points. How many of each type of question is on the test? (12 pts)

Answer 1

19 questions, 6 pointers and 4 pointers

6x + 4y = 100

x + y = 19

4x +4y = 4(19) = 76

subtract last equation from the first to get

2x = 24

x = 12 questions worth 6 points each

y = 19-12 = 7 questions worth 4 points each

7(4) +12(6) = 28 +72 = 100