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Hi there! Have questions about your homework? At Brainly, there are 60 million students who want to help each other learn. Questions are usually answered in less than 10 minutes. Try it for yourself by posting a question! :D

Firstly find the total marks i.e. equal to 180X4=720 now , he hav scored 450 marks so marks deducted=720-450=270 now ,these for each wrong or unattempted question marks deducted is 5 as 4 of the question and 1 of the negative marking,so no.of questions wrong or unattempted is 270/5 = 54 therefore no. of answers correct =180-54=126

Let, no. of correctly done questions = x no of wrong answered question & un-attempted questions = y a/q, total questions = 180=x+y---------------eqn(1) 4x-y=450----eqn(2) eqn(1)+eqn(2) 5x=630 x = 126 y=180-126=54 therefore 126 questions correctly done.