$a \%$ of $b + b \%$ of $a =$

If $35 \%$ of $A$'s income is equal to $25 \%$ of $B$'s income,then the ratio of $A$'s income to $B$'s income is

If $x$ $\%$ of $y$ is $100$ and $y$ $\%$ of $z$ is $200,$ then find a relation between $x$ and $z$.

$A, B, C$ are three students. $A$ got $18 \%$ more marks than $B$ and $12 \%$ less than $C$. If $B$ got $220$ marks,how many marks did $C$ get?

The sum of two numbers is $2490$. If $6.5\%$ of one number is equal to $8.5\%$ of the other,then the numbers are:

From a container having pure milk,$20 \%$ is replaced by water and the process is repeated thrice. At the end of the third operation,the milk is: (in $\%$ pure)