Telescience help.

[SeMiPL1]

Your desired X and Y are at the front of the equation. So for an example on the wiki and using your numbers:
35=3*x+26
So to rearrange this:
(35-26)/3=x, where x is the required x coordinate
This same idea is applied to Y, so you just have to rearrange the formula so that it subtracts your 'c' from your desired and then divides it by your 'm'

I made a spreadsheet that does everything for me, it ends up being quicker this way.

Thanks. Everything is working fine right now!