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.

Let x be the speed of boat.

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

4x-24=10x+60.

6x=84.

x=84/6.

=14 km/h.

Speed of boat =14km/h.