$x$ number of men can finish a piece of work in $30$ days. If there were $6$ men more,the work could be finished in $10$ days less. The actual number of men is

$A$ 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?

$A$ can do a piece of work in $4 \, days$ and $B$ can do it in $12 \, days.$ In how many $days$ will they finish the work,both working together?

$P$ and $Q$ together can do a job in $6$ days. $Q$ and $R$ can finish the same job in $60/7$ days. $P$ started the work and worked for $3$ days. $Q$ and $R$ continued for $6$ days. Then the difference of days in which $R$ and $P$ can complete the job is

$A$ can do a certain work in the same time in which $B$ and $C$ together can do it. If $A$ and $B$ together could do it in $10 \text{ days}$ and $C$ alone in $50 \text{ days}$,then $B$ alone could do it in (in $\text{days}$):

$A$ and $B$ together can do a piece of work in $30$ days. $A$ having worked for $16$ days,$B$ finishes the remaining work alone in $44$ days. In how many days shall $B$ finish the whole work alone?