Step-by-step explanation:
the height from the 90° angle (which is y here) in a right-angled triangle is the square root of the Sergent lengths of the Hypotenuse.
y = sqrt(3×9) = 3×sqrt(3)
and x we get via Pythagoras :
x² = y² + 9² = 27 + 81 = 108
x = sqrt(108) = sqrt(36×3) = 6×sqrt(3)
so, A is correct.
