Answer:
30
Explanation:
A player answers x correct questions and y incorrect questions for a total of 40 questions.
x + y = 40
The score is obtained by subtracting y incorrect answers from two times the x of correct answers. The player's score is 50.
2x - y = 50
Use substitution to solve. Rearrange the first equation so that it is equal to y. Then, substitute the y-value into the second equation.
x + y = 40
y = 40 - x
2x - y = 50
2x - (40 - x) = 50
2x - 40 + x = 50
3x - 40 = 50
3x = 90
x = 30
Since x was made to represent correct answers, the player had 30 correct answers.