Answer:
The length of the missing leg is 12
Explanation:
Right Triangles
A right triangle is a triangle that has an internal angle of 90°. In right triangles, the Pythagorean relation between its side length stands.
Suppose a and c are the smaller sides, also called 'legs' of the triangle, and b is the bigger side, also known as hypotenuse, then:

We are given the hypotenuse b=13 and one leg c=5. Let's find the missing leg solving the above equation for a:

Substituting:


Solving:

The length of the missing leg is 12