For the first question the problem is simple. He is essentially going around 2 sides of a triangle, instead of along the hypotenuse. You would have to use Pythagoras' theorem for the real answer, a^2 + b^2 = c^2. However, for question 15, i don't know, I'm pretty sure this is an American question and I'm British, I don't believe I have ever encountered ordered pairs, or at least i don't remember learning them. Hope this helps ;)
