Explanation:

ari scored 45% marks and failed by 18 marks
pass mark of the class = 45%of total mark + 18
Rama scored 54% marks and get 27 marks more than the passing marks
pass mark of the class = 54% of total mark - 27
total marks = x

Here passing marks equal. So,
45 % of x+ 18 = 54 % of x-27
18 + 27 = (54 — 45) % of x
45 = 9 % of x
x = 45*(100/9) = 500
Rohan's mark = 75/100* 500 = 375