The easiest way to work with linear equation is the desktop software Algebrator.  As an example of simplifying the distance between two points, the following entry into doyourmath.com solves for the distance, 'd':

Click to see all the steps

The answer can be provided either as an integer (an exact answer) or a decimal number (an approximation of the answer):

To help you clearly understand our desktop software and how appropriate it may be for your needs, please use one of the following links to obtain a free trial of the program:

Windows: http://www.softmath.com/tr/alg51win-tr-en.exe

Mac: http://www.softmath.com/tr/alg51mac-tr-en.dmg