Answer:
After 11 seconds the hovercraft will land on ground
Explanation:
Given function that shows the height of a hovercraft,

Where,
x = number of second.
When the hovercraft land the ground,



By zero product property,
x - 11 = 0 or x + 3 = 0
⇒ x = 11 or x = -3 ( not possible ),
Hence, after 11 seconds the hovercraft will land on ground.