If it is a distance, there are two formulas: point (x 1, y 1) to straight line ax+by+c = 0d = | ax1+by1+c |/root sign (Party A+Party B).

If the distance between two parallel straight lines is Ax+By+C 1=0, and Ax+By+C2=0, then d=|C 1-C2|/ root sign (Party A+Party B).

Directly to the distance between two points, you know?