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

The price of cooking oil has increased by $25 \%$. The percentage of reduction that a family should effect in the use of cooking oil,so as not to increase the expenditure on this account,is (in $\%$)

The $75 \%$ of a number is $380$ more than $35 \%$ of the same number. What is $20 \%$ of that number?

The number which exceeds $16 \%$ of it by $42$ is:

An army lost $10 \%$ of its men in war,$10 \%$ of the remaining due to diseases,and $10 \%$ of the rest were hurt. Thus,the strength was reduced to $729000$ active men. Find the original strength.

The population of Delhi increases by $10 \%$ every year. If the current population of Delhi is $1,331,000$,what was its population $3$ years ago?