averages Questions

The average monthly income of $A$ and $B$ is $\text{Rs. }1400$, that of $B$ and $C$ is $\text{Rs. }1560$ and of $A$ and $C$ is $\text{Rs. }1440$. The monthly income of $C$ is:

The average of $9$ numbers is $30$. The average of the first $5$ numbers is $25$ and that of the last $3$ numbers is $35$. What is the $6^{\text{th}}$ number?

The average salary of male employees in a firm was $\text{Rs. }52$ and that of female employees was $\text{Rs. }42$. If the mean salary of all the employees was $\text{Rs. }50$, what was the percentage of female employees?