Answer is :
6.778 meters.
Step-by-step explanation:
y = u t + 1/2 at²
6 m = u sinθ + 1/2 at²
6 m = (12) sin 30°t + 1/2 (9.81)t²
4.905 t² + 6 t -6 = 0
By solving, t = 0.6522 s.
The horizontal distance :
x = u cosθ t
= (12) cos 30° (0.6522)
= 6.778 meters.