Answer:
The percent decrease is approximately 
(Don't know what you are expected to round to.)
Step-by-step explanation:
Percent change can be calculated by doing:

Then you multiply the result to covert it to a percentage.
Let's use this formula:




approximately
Now the answer as a percent is
approximately.
The percent decrease is approximately 
Answer:
D, the last answer choice
Step-by-step explanation:
y=mx+b is the formula. 2/3x is the slope and 3 is the y intercept.
Given:
descends at a rate of 320 feet per minute for 3 minutes.
320 feet per minute * 3 minutes = 960 feet
Total change in altitude is 960 feet. Since it is descending, I believe it would be a negative 960 feet.