Answer: B) 10 three-point questions and 14 five-point questions
Explanation:
x represents three-point questions
y represents five-point questions
3x + 5y = 100 → 1(3x + 5y = 100) = 3x + 5y = 100
 x + y = 24 → -3(x + y = 24) =  -3x -3y = -72 
 2y = 28
 y = 14 (five-point questions) 
x + y = 24
x + 14 = 24
 x = 10 (three-point questions)