These types of problems are best suited for Algebrator, as they allow you to explore the algebraic setup for such problems.  The images appended to this show how the Line Wizard for "Parallel line passing through a point" is entered and then also shows how the solution is obtained (the solution can be obtained through doyourmath.com by entering in the solution, but the setup for such a problem is tailored for Algebrator). 

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