Answer is 14.14
Reason
Using Pythagorean theory
a^2 + b^2 = c^2
The two legs are a and b, the longest diagonal opposite the right angle is c
10^2 + 10^2 = c^2
200 = c^2
Take square root of both sides
14.14 = c
Do the parentheses first
Since it’s dividing you are supposed to times it