Alvin paddled for 4 hours with a 6-km/h current to reach a campsite. The return trip against the same current took 10 hours. Find the speed of the boat in still water. What is the speed of the boat in still water in km/h?

Let "x" be the speed of boat in still water

distance = speed * time

4(x+6)=10(x-6)

4x+24=10x-60

6x=84

x=14 km/h  is the speed of boat