Respuesta :

x^2 = 9^2 + 12^2
x^2 = 81 + 144
x^2 = 225
x = 15

answer is C. 15

Step-by-step explanation:

Using pythagoras theorem :

x² = 12² + 9²

x² = 144 + 81

x² = 225

x = 15