to find the answer. you have to use the pythagorean theorem.
a² + b² = c² where "a" and "b" are the legs and "c" is the hypotenuse.
24² + b² = 26²
576 + b² = 676
b² = 676 - 576
b² = 100
√b² = √100
b = 10 so 10 is the number of the second leg.
hope this helps, God bless!