Answer: the player answered 30 questions correctly.
Explanation:
Let x represent the number of questions that the player answered correctly.
Let y represent the number of questions that the player answered incorrectly.
The number of questions that the player answered is 40. It means that
x + y = 40- - - - - - - - - - -1
The score on the trivia game is obtained by subtracting the number of incorrect answers from twice the number of correct answers. If the player obtained a score of 50, It means that
2x - y = 50
y = 2x - 50
Substituting y = 2x - 50 into equation 1, it becomes
x + 2x - 50 = 40
3x - 50 = 40
3x = 40 + 50 = 90
x = 90/3
x = 30