Answer:
30 ft
Explanation:
The Pythagorean theorem can be used to find the length of the unknown side. It tells you the sum of the squares of the legs is equal to the square of the hypotenuse.
12² +a² = 13²
a² = 169 -144 = 25
a = √25 = 5
The sum of the side lengths is ...
(12 +5 +13) ft = 30 ft
The perimeter is 30 feet.