When $40$ is subtracted from $30 \%$ of a number,the result is $50$. What is the value of the number?

The population of a town increases by $12 \%$ during the first year and decreases by $10 \%$ during the second year. If the present population is $50400$,what was it $2$ years ago?

Sweta invested $Rs. 10,000$ in a scheme exactly three years ago. The value of the investment increased by $10\%$ during the first year,increased by $5\%$ during the second year,and decreased by $10\%$ during the third year. What is the value of the investment today?

$x$ is $30 \%$ more than $y$ and $25 \%$ less than $z$. If the value of $y$ is $₹ 300$,then what is the value (in $₹$) of $z$?

Sameer spends $24 \%$ of his monthly income on food and $15 \%$ on the education of his children. Of the remaining salary,he spends $25 \%$ on entertainment and $20 \%$ on conveyance. He is now left with $₹ 10736$. What is the monthly salary of Sameer?

The price of cooking oil has increased by $15 \%$. 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: