$5$ men or $7$ women can earn $Rs. 5,250$ per day. How much would $7$ men and $13$ women earn per day? (in $Rs.$)

$A$ does a work in $10$ $days$ and $B$ does the same work in $15$ $days$. In how many $days$ will they together do the same work?

Hemant decided to build a farmhouse in $40$ days. He employed $100$ men in the beginning and $100$ more after $35$ days and completed the construction in the stipulated time. If he had not employed the additional men,how many days behind schedule would it have been finished? (in days)

Working efficiencies of $A$ and $B$ for completing a piece of work are in the ratio $3: 4$. The number of days taken by them to complete the work will be in the ratio:

$A$ can do a piece of work in $12$ days and $B$ in $15$ days. They work together for $5$ days and then $B$ leaves. The number of days taken by $A$ to finish the remaining work is:

$A$ 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)