Answer:
13
Explanation:
This is a special right triangle with side lengths 5-12-13 respectively.
If we can't remember the lengths we can use the following formula to calculate the lentgh of hypotenuse:

the sum of square measure of both legs is equal to the square measure of hypotenuse

25 + 144 = c^2
169 = c^2 find the root of both sides
13 = c, hypotenuse.