$A$ can do a piece of work in $20$ days and $B$ in $30$ days. They work together for $7$ days and then both leave the work. Then $C$ alone finishes the remaining work in $10$ days. In how many days will $C$ finish the full work?

$A$ man can do a piece of work in $5$ days,but with the help of his son,he can do it in $3$ days. In what time can the son do it alone? (in days)

$A$ alone can complete a work in $16$ days and $B$ alone in $12$ days. Starting with $A$,they work on alternate days. The total work will be completed in (in days):

$4$ men or $6$ women can finish a piece of work in $20$ days. In how many days can $6$ men and $11$ women finish the same work?

$A$ man,a woman,and a boy can together complete a piece of work in $3$ days. If a man alone can do it in $6$ days and a boy alone in $18$ days,how long will a woman alone take to complete the work? (in days)

$A$ daily wage earner gets a daily wage at the rate of $Rs. 150$ per day,subject to the condition that he will have to pay a penalty at the rate of $Rs. 25$ per day for the days he is absent. At the end of $60$ days,he receives an amount of $Rs. 7,600$. The number of days he worked is: