Mitch has saved $20000 to finance his boating hobby. A new boat costs $1500 per foot in length. If Mitch needs to keep $500 for a license and registration, and three times that amount for docking fees, how many feet is the longest boat he can buy?
Mitch needs to keep 500 * 3 = 
<gadget id="calculator">500*3</gadget>
<output>1_500</output>
1500 for docking fees.
Thus, he needs to keep 500 + 3 * 500 = $
<gadget id="calculator">500+3*500</gadget>
<output>2_000</output>
2000 for license, registration, and docking fees.
He has 20000 - 2000 = $
<gadget id="calculator">20000-2000</gadget>
<output>18_000</output>
18000 left to spend on a boat.
Therefore, the longest boat he can buy is 18000 / 1500 = 
<gadget id="calculator">18000/1500</gadget>
<output>12</output>
12 feet long.

<result>12</result>