Answer: y = 5 feet long.
Step-by-step explanation:
To solve this, you can use the Pythagorean theorem:
[tex]a^2 + b^2 = c^2\\a^2 + 12^2 = 13^2\\a^2 + 144 = 169\\a^2 = 25\\a = 5[/tex]
The side length y is equal to 5.
