How do I solve this word problem

Question

The Connecticut River flows at a rate of 4 km/hr. In order for a cruiser to travel 60 km upriver and in a total of 8 hr, how fast must the boat be able to travel in still water?

Answer 1

Let x = boat's speed in still water in km/hr

 

Boat's speed upriver = x - 4

 

Distance = (rate)(time).  So, 60 = (x - 4)(8).

                                         60 = 8x - 32

                                         92 = 8x

So, x = 11.5 km/hr. 

Answer 2

Find the speed of the boat by dividing 60 km by 8 hours, which is 7.5 km/hr. Since during all this time the river was working against the boat with a speed of 4 km/hr. You add that together to make 11.5 km/hr, that is the speed the boat would have to be able to go in still water.