Help! Coordinates of intersecting lines!

[Mast4rwang]

Hello, it seems I forgot how to math
Could anyone help me with finding a formula to solve this task? And if it's not too complicated, is it possible to make a universal formula which would work with dots placed in any of the 4 quadrants?

 

[tkhunny]

This requires a little algebra. Please show your best efforts.

 

[Mast4rwang]

Thanks, that word actually helped me a lot I used to be good at functions but I haven't used it for so long that I need to see actual solved examples to refresh memory. These sites did the trick, thanks again


http://www.coolmath.com/algebra/08-lines/12-finding-equation-two-points-01
http://www.mathopenref.com/coordintersection.html