Mark has two pets, a hare that runs 10 feet/second and a turtle that crawls 1 foot/second. If they're going to run a 20 foot-race, how much of a head start (in seconds) does the turtle need to finish in a tie?
We can find how long the hare spends running by dividing the distance of the race by the hare's speed: 20 feet / 10 feet/second = 
<gadget id="calculator">20/10</gadget>
<output>2</output>
2 seconds.
We can do the same for the turtle: 20 feet / 1 foot/second = 
<gadget id="calculator">20/1</gadget>
<output>20</output>
20 seconds.
Finally, subtract the hare's run time from the turtle's run time to find the length of the head start the turtle needs: 20 seconds - 2 seconds = 
<gadget id="calculator">20-2</gadget>
<output>18</output>
18 seconds.

<result>18</result>