First of all, you could just count the units, but that's not really too effective. Otherwise, you could start from the coordinates of the "C" point, and see how it's at -Y = -5. Therefore, to get to the line separating the two points, you would have to subtract 5 from 5 to get to the line. Now, you look at point "A". It's Y coordinate is 2. Therefore, adding 5 and 2 together gives you 7 units.
