Unless
---Select---
indicate otherwise, multiplications are done before additions.

"Use Pythagorean Theorem to solve (a right triangle with the base being one of the side lengths and the height being the other side length.  a^2 + b^2 = c^2
64^2 + 100^2 = length of diagonal ^2
4096 + 10000 = 14096
The length of the diagonal is the square root of 14096 or 118.727 meters (rounded to the thousandths place). "
 Read more on -

the answer is credited to the user on in the link

hope this helps!!