If Rs. $2800$ is $\frac{2}{7}$ of the value of a house,what is the total worth of the house (in Rs.)?

In a test,a candidate secured $468$ marks out of maximum marks $A$. If the maximum marks $A$ were converted to $700$ marks,he would have secured $336$ marks. What were the maximum marks of the test?

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 $\%$)

$40 \%$ of $? = 240$

In an examination,$65 \%$ of students passed in Civics and $60 \%$ in History,while $40 \%$ passed in both of these subjects. If $90$ students failed in both History and Civics,then what is the total number of students?

The income of a company increases $20 \%$ per annum. If its income is $Rs$ $42664000$ in the year $1999$,what was its income in the year $1997$?