Motion Questions

The ratio between the speed of travelling of A and B is $2:3$ and therefore A takes $15$ minutes more than the time taken by B to reach a destination. If A had walked at double the speed, how long would he have taken to cover the distance?

A boat goes $80\text{km}$ upstream in $16$ hours and $72\text{km}$ downstream in $12$ hours. The speed of the boat in still water is: