Until you figure out how far the other side is.
This is a dynamicization of a puzzle found at the Futility Closet.
[url]http://www.futilitycloset.com/2014/01/30/in-a-word-454/[/url]
It sets up with random but reasonable numbers each time. I probably should have set it up as ferries to Mackinac Island with Arnold's and Shepler's ferries, but maybe for version 2.
I love these algebra problems that look like they don't have enough information. This reminds me of NRICH's burning candle problem ([url]http://www.geogebratube.org/material/show/id/10226[/url]) or the Escalator problem ([url]http://www.geogebratube.org/material/show/id/14703[/url]).