To find this, we look at our angles. ∠e and ∠b are what we call alternate exterior angles. These are basically just angles on the outside of the traversals, when added with each other, equal 180°. This may sound complicated, but it is fairly easy.
All you have to do is take 180 and subtract it from ∠e.
Okay, so if e=110, then so does c, because they are Alternate Interior angles. If c=110, then so does a, because they are Alternate Exterior. Angles a and b are on a straight line, which equals 180 altogether, and 180-110 is 70, so the measure of angle b is 70.
Counting each visible cube, and multiplying it by 2, he used 112. If you counted them, there would be 56 cubes. You'd multiply by 2 for the non-visible ones.
