If two-third of $A$ is four-fifth of $B ,$ then $A : B =?$

Three numbers $A, B$ and $C$ are in the ratio of $12: 15: 25$. If the sum of these numbers is $312$,find the ratio between the difference of $B$ and $A$ and the difference of $C$ and $B$.

If $33 \%$ of $A$ is equal to $55 \%$ of $B$,then find the ratio of $A$ and $B$.

The ratio of the numbers of boys and girls of a school with $504$ students is $13: 11$. What will be the new ratio if $12$ more girls are admitted?

Two numbers are respectively $20 \%$ and $50 \%$ more than a third number. The ratio of the two numbers is

The students in three classes are in the ratio $4:6:9$. If $12$ students are increased in each class,the ratio changes to $7:9:12$. Then the total number of students in the three classes before the increase is