If $P \%$ of $P$ is $36,$ then $P$ is equal to

Two-fifths of one-third of three-seventh of a number is $15$. What is $40$ per cent of that number?

$A$ person's salary has increased from $Rs. 7200$ to $Rs. 8100$. What is the percentage increase in his salary (in $\%$)?

Mr. Katial buys a house for ₹$100000$ and rents it out. He puts $12.5 \%$ of each month's rent aside for upkeep and repairs,pays ₹$325$ per year as taxes,and realizes a $5.5 \%$ annual return on his investment. Find the monthly rent.

If $35 \%$ of a number is $12$ less than $50 \%$ of that number,then the number is:

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