Respuesta :

Answer:

x = 12.

Step-by-step explanation:

This is a right angled triangle so you use the Pythagoras Theorem:

15^2 = 9^2 + x^2

x^2 = 15^2 - 9^2

x^2 = 225 - 81

x^2 = 144

x = √144

x = 12.