Debbie traveled by boat 5 miles upstream to fish in her favorite spot. Because of the 4 mph current, it took her 20 minutes longer to get there than to return. How fast will her boat go in still water?

MY WORK:

Let A = against the current

Let W = with the current

The boat will travel faster with the current and slower against the current.Is this correct?

Here is my set up:

...........rate..........time........distance

A.......(x+4).....(x + 20)........(x+4)(x+20)

W.......(x-4).......(x)..............(x-4)(x)

Since the distance she travelled both ways is the same, I set up the following equation:

(x+4)(x+20) = (x-4)(x)

The letter x here represents the speed of the boat in still water.

Is any of this correct?

If not, what did I do wrong?