Use the Pythagorean Theorem to solve for the value of x

Step-by-step explanation:
Pythagoras
c² = a² + b²
with c being the Hypotenuse (the side opposite of the 90 degree angle).
x² = 12² + 9² = 144 + 81 = 225
x = 15 ft
so, the first answer option is correct.