1) Since we have a right triangle we can use the Pythagorean Theorem to solve and find, with a little adjustment.
The Pythagorean Theorem states
a²=b²+c² Given a is the hypotenuse, not the case in this problem
So we can rewrite it as
c² = a²+b² Because the hypotenuse is opposite to the right angle
25² =a²+24²
625= a² +576
625 -576 = a²
49=a²
√49 =√a²
a =+7, -7 In this case -7 is not convenient
a=7