Answer:
The height of the rocket at 3 seconds is 270 feet
Step-by-step explanation:
To calculate the height of the rocket at 3 seconds,
First, we will determine the height the rocket has traveled in 3 seconds 
The height traveled by the rocket is given by 
Height (h) = Velocity (v) × Time (t) 
From the question, 
The rocket travels 85 feet per second, that is the velocity of the rocket is 85 feet per second, 
Now, 
v = 85 feet / second 
t = 3 seconds 
Hence, 
Height (h) = 85 feet /second × 3 seconds
Height = 255 feet
∴ the rocket would have traveled 255 feet in 3 seconds,
But, the rocket starts on a launch pad 15 feet of the ground,
Then, the height of the rocket at 3 seconds is 
255 feet + 15 feet = 270 feet.
Hence, the height of the rocket at 3 seconds is 270 feet