If in an examination $20 \%$ students failed in Hindi,$25 \%$ failed in English,and $7 \%$ failed in both subjects,then what is the percentage of students who failed in at least one of the subjects (in $\%$)?

Rita invested $25 \%$ more than Sunil. Sunil invested $30 \%$ less than Abhinav who invested $Rs. 6000$. What is the respective ratio between the amount that Rita invested and the total amount invested by all of them together?

Aditya's salary is $125\%$ of Ram's salary. Sanjay's salary is $80\%$ of Ram's salary. If the total of all the three salaries is $Rs. 61000$,what is Sanjay's salary?

In a History examination,the average for the entire class was $80$ marks. If $10 \%$ of the students scored $95$ marks and $20 \%$ scored $90$ marks,what was the average marks of the remaining students of the class?

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

$A$ businessman imported laptops worth $Rs$ $210,000$,mobile phones worth $Rs$ $100,000$,and television sets worth $Rs$ $150,000$. He had to pay $10\%$ duty on laptops,$8\%$ on phones,and $5\%$ on television sets. How much total duty (in Rupees) did he have to pay on all items as per the above details?