Coordinate Joker is a Geocaching Add-on for application Locus Map but works also with other apps that can display waypoints from a gpx kml or kmz file.

Finally you made it to the pre-final after 3 hours and several miles. A final number to be determined: Count the planks of the bridge ... Hey where has the bridge gone?! It was replaced by a pipe beneath the ground. What now ...? Look up the logs for potential telephone jokers? No then I'd rather draw a line in my map where the final could be located given the formula and missing x ...
But wait - Coordinate Joker will do it for you. Just enter the coordinate formulas and it will send the resulting waypoints to your preferred Geocaching app. With a bit of luck one point will appear close to some path while the others may be far away. Then where would you look for the final? :)