$A$ and $B$ can do a piece of work in $12 \, \text{days}$ and $15 \, \text{days}$ respectively. They began to work together,but $A$ left after $4 \, \text{days}$. In how many more $days$ would $B$ alone complete the remaining work?

$P$ can complete a work in $12$ days working $8$ hours a day. $Q$ can complete the same work in $8$ days working $10$ hours a day. If both $P$ and $Q$ work together,working $8$ hours a day,in how many days can they complete the work?

Ram can finish a work in $15 \text{ days}$ working $8 \text{ hrs/day}$. Fari can finish it in $6 \frac{2}{3} \text{ days}$ at $9 \text{ hrs/day}$. Find in how many days both can finish it together,if both work $10 \text{ hrs/day}$?

The work done by a woman in $8\, \text{hours}$ is equal to the work done by a man in $6\, \text{hours}$ and by a boy in $12\, \text{hours}$. If working $6\, \text{hours per day}$,$9$ men can complete a work in $6\, \text{days}$,then in how many $\text{days}$ can $12$ men,$12$ women,and $12$ boys together finish the same work working $8\, \text{hours per day}$?

$A$ can finish a work in $18$ days and $B$ can do the same work in $15$ days. $B$ worked for $10$ days and left the job. In how many days can $A$ alone finish the remaining work?

$A$ can do a piece of work in $120$ days and $B$ can do it in $150$ days. They work together for $20$ days. Then $B$ leaves and $A$ alone continues the work. After $12$ days,$C$ joins $A$ and the work is completed in $48$ days more. In how many days can $C$ do it if he works alone?