The maximum possible score in an exam was 80 and all questions carried equal weightage. For each correct answer 4 marks were awarded whereas for each wrong answer 1 mark was deducted. For no answer, the marks remained unchanged. A student got 57 marks in which he failed to attempt only 3 questions. Answer the number of questions he got correct as a percentage of total number of questions.

Answer 1

r + w =77 because he didn't answer 3
4r -1w = 57

5r =132 can you finish from here?

Answer 2

I misstype 3 instead of 2 question which he failed to attempt.
Thanks.75%