Question 9363
Let's call the time it takes to catch up x. 
The walker will travel 3 miles for each hour, or 3x.
The rafter will travel 9 miles for each hour, or 9x.
But the walker starts an hour earlier, so the walker has walked for x+1 hours.
When the rafter catches up, it means they have each traveled the same distance from the start, so 3(x+1) = 9x. 
This reduces to 3x + 3 = 9x, and 3 = 6x. 
So what is x?
That's how many hours it takes for the rafter to catch up. [Hint: it's only a fraction of an hour] 
And now, how far will each of them go in that time? It better be the same distance!