It depends on the quality of the balls. It also depends on where you are buying them. Do you have any more details?
Answer:
15 miles
Step-by-step explanation:
Let's say the dock is at the origin on a coordinate plane and each unit is 1 mile. If the boat travels 9 mile due north, that means that we move up from the origin (0, 0) 9 units to point A (0, 9). Now, this boat moves 12 miles due west, so we will go 12 units to the left of (0, 9) to point B (-12, 9). See the attached drawing (sorry for the crudeness).
Notice that this is a right triangle with legs of 9 and 12. That means the distance from the boat to the dock is just the hypotenuse, so use the Pythagorean Theorem: distance = 
Thus, the answer is 15 miles.
Hope this helps!
20.50 is the amount patti is making per hour
The final answer would be:
9x / (x-8)
The exact steps are shown in the attached picture.
Note that when dividing two fractions, we convert the division into multiplication and flip the second term.