If $x$ men can do a piece of work in $x$ days,then the number of days in which $y$ men can do the same work is (in days)

$A$ can do a work in $10 \text{ days}$ and $B$ in $20 \text{ days}$. If they work together on it for $5 \text{ days}$,then the fraction of the work that is left is:

$A$ and $B$ can complete a work in $15$ days and $10$ days respectively. They started doing the work together,but after $2$ days $B$ had to leave and $A$ alone completed the remaining work. In how many days was the whole work completed?

$A$ alone can complete a work in $18 \, days$ and $B$ alone in $15 \, days.$ $B$ alone worked at it for $10 \, days$ and then left the work. In how many more days will $A$ alone complete the remaining work?

$A$ completes a piece of work in $4 \text{ days}$ and $B$ completes it in $6 \text{ days}$. If they both work on it together,then the number of days required to complete the same work is (in $\text{days}$):

If $3$ men or $6$ women can do a piece of work in $16$ days,in how many days can $12$ men and $8$ women do the same piece of work? (in days)