Bolts are usually classified in terms of two types of measurements: the metric system and the imperial system. In calipers, the metric system is in units of millimeters, while the imperial system is in units of inches. For example, when a bolt is sized as 12 × 1.25 in the metric system, that means the bolt thread diameter measures 12 mm, and the thread pitch measures 1.25 mm.
So, if your metric bolt measures 0.78 over the threads, that means that the
size of the bolt is 0.78 mm in thread pitch. The attached picture shows how you measure the thread pitch.
This equation can have a number of solutions. Typically when solving a two-variable equation, you are looking for the slope intercept form of the line. In this case that is:
y = 3x - 1
My guess would be distributive. i maybe be wrong so don't get mad if I'm wrong.