Answer:
15
Pythagorean Theorem:
[tex]a^2 + b^2 = c^2[/tex]
Step-by-step explanation:
[tex]1)\ x^2 = 9^2 + 12^2 = 81 + 144 = 225[/tex]
[tex]2)\ x = \sqrt{225} = 15[/tex]
