I need help am bad at math

Answer:
14 ft
Step-by-step explanation:
a² + b² = c²
a=5
b= unknown
c= hypotnuse (13)
5² =25
13²=169
subtract 25 from 169 to get 144. Then take the square root of 144.
You should get 12. Dont forget to add the extra length
14 is the answer