Answer:
A
Step-by-step explanation:
Using Pythagoras' identity in the right triangle.
The square on the hypotenuse is equal to the sum of the squares on the other 2 sides, that is
BC² = 9² + 12² = 81 + 144 = 225 ( take the square root of both sides )
BC = [tex]\sqrt{225}[/tex] = 15 → A
