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