If $₹ 2800$ is $\frac{2}{7}$ percent of the value of a house,the worth of the house (in $₹$) is

In an election between two candidates,one got $52 \%$ of the total valid votes. $25 \%$ of the total votes were invalid. The total number of votes were $8400$. How many valid votes did the other person get?

The population of a town is $9000$. If the number of females increases by $5 \%$ and the males by $7.5 \%$,what will be the total population after the increase? The number of females currently is $3000$.

$x \%$ of $y + ? \%$ of $x = x \%$ of $(x + y)$

The population of a town increases by $2.5 \%$ annually but decreases by $0.5 \%$ every year due to migration. What will be the net percentage increase in population after $2$ years (in $\%$)?

An $HR$ Company employs $4800$ people,out of which $45 \%$ are males and $60 \%$ of the males are either $25$ years or older. How many males are employed in the company who are younger than $25$ years?