Let number of girls and boys be 3x and 2x respectively. Given, 3x−2x=30 Or x=30. So the number of students =3x+2x=5x=150. Also, number of girls (3x) and boys (2x)=90 and 60 respectively. Number of students pass the exam =68% of 150=102. Number of girls pass the exam =102−30=72. Therefore, number of girls who fail in the exam =90−72=18 Hence, percentage of girls fail the exam =