There are 180 multiple choice questions in a test. If a candidate gets 4 marks for every correct answer and for every unattempted or wrongly answered question one mark is deducted from the total score of correct answers. If a candidate scored 450 marks in the test, how many questions did he answer correctly?
Let the number of correct answers are 
Number of wrong answered questions are 
Total score due to right answers = 
Marks deducted due to wrong answers = 
According to question:
Therefore number of correct questions are 126
17