Exam is worth 145 points 50 questions. some are 2 points and some are 5. how many question are 5 and how many are 2

Let x = number of questions worth 2 and y be  those worth 5.

so we have the system:-

x + y = 50
2x + 5y = 145

multiply first equation by -2:-

-2x - 2y = -100

Add this to the second equation:-

3y = 145-100

3y = 45
y = 15 

and x = 50-15 = 35

-  there are 35 questions worth 2 points and 15 worth 5 points.

The answer to this question is c