Two numbers are respectively $20 \%$ and $10 \%$ more than a third number. How much per cent is the first number more than the second?

$40 \%$ of $1640 + ? = 35 \%$ of $980 + 150 \%$ of $850$

Sashi has $Rs. 90000$ with him. He purchases a mobile,an iPad,and a laptop for $Rs. 15000$,$Rs. 13000$,and $Rs. 35000$ respectively and puts the remaining money in his bank account which pays $15 \%$ per annum compound interest. After $2$ years,he sells off the three items at $80 \%$ of their original price and also withdraws his entire money from the bank by closing the account. What is the total percentage change in his assets (in $\%$)?

If $30 \%$ students failed in English,$45 \%$ failed in Math,and $25 \%$ failed in both,then what is the percentage of students who passed in both subjects (in $\%$)?

If $37 \frac{1}{2} \%$ of a number is $45,$ then $87 \frac{1}{2} \%$ of the number will be:

In a class,$60 \%$ of the students pass in Hindi and $45 \%$ pass in Sanskrit. If $25 \%$ of them pass in both subjects,what percentage of the students fail in both subjects?