In an objective competitive exam, a correct answer score 4 marks and on a wrong answer 2 marks are negatively added. A student scores 420 marks from 150 question. How many answers were correct ?  Choose the correct choice from the following options
A) 150
B) 155
C) 140
D) 120
E) 165
let x be the correct answer and y be the wrong answer   so the total number of questions is (x + y) = 150.....(1)   =&gt; 4x - 2y = 420.....(2)   By solving (1) &amp; (2), we get   =&gt; 6x = 720   hence x = 120   Therefore, number of correct answers are 120.   Answer 120
<result>D</result>
In an objective competitive exam, a correct answer score 4 marks and on a wrong answer 2 marks are negatively added. A student scores 420 marks from 150 question. How many answers were correct ?