This is a form of the Pythagorean Theorem. We just need to know how far we went in the x direction and how far in the y direction then use
a^2 + b^2 = c^2 to find the value.
distance in the x direction (-4 to -4) that's easy it didn't move. so that is zero and thus would make the distance all in the y direction.
To move from 8 to -8 we take (8 - (-8)) = 8 + 8 = 16 which is your answer