Can someone please help me please please. They are using the pythagorean thm. a^2 + b^2 = c^2

So for the 4th question the answer should be 25 as the triangle is just an multiplicative of the 3,4,5 triangle.
And for the 5 question the answer should be 8 as the square root of 10^2-6^2 is square root 64 which is 8