Question

in a competetive examination,a candidate scores 5 marks for each correct answer and looses 2 marks for every wrong answer.if he attempts 85 question and scores 285 marks,find the number of questions he attempts correctly

Answer 1

let no. of correctly solvd questions b x n those of incorrect b y
so x + y = 85
5x - 2y = 285
on solving these equations u'll get x = 65 

Answer 2

no of questions answerd=x
no of questions which are incorrect=y
so  as  per the question
x + y = 85 (1)
5x - 2y = 285(2)
from one y =85-x (3)
by substitution equation 3 in 2 you get
5x-2 (85-x)=285
5x-170+2 x=285
7x=285+170
7x=455
x=65
so no  of correct answers =65
and no of incorrect answer =85-65
                                         =20