Express $8 \frac{1}{3} \%$ as a fraction.

If $60 \%$ of the students in a school are boys and the number of girls is $812$,how many boys are there in the school?

Two numbers $A$ and $B$ are such that the sum of $6\%$ of $A$ and $4\%$ of $B$ is two-thirds of the sum of $6\%$ of $A$ and $8\%$ of $B$. Find the ratio of $A:B$.

What percent of Rs. $2650$ is Rs. $1987.50$?

One number is $25 \%$ of another number. The larger number is $12$ more than the smaller. The larger number is

$A$ jar contains $10$ red marbles and $30$ green ones. How many red marbles must be added to the jar so that $60 \%$ of the marbles will be red?