Percentage of Girls Who Do Not Pass

Let total students be $100x$. Girls $= 60x$, Boys $= 40x$. Given $60x - 40x = 30 \implies 20x = 30 \implies x = 1.5$. Total students $= 150$, Girls $= 90$, Boys $= 60$. Total passed $= 68\%$ of $150 = 102$. Passed boys $= 30$, so passed girls $= 102 - 30 = 72$. Girls who did not pass $= 90 - 72 = 18$. Percentage of girls who did not pass $= \frac{18}{90} \times 100 = 20\%$.