Answer:
Since, an airplane descended 4,000 feet before landing.
Now, we have to determine the integer which represents the number of feet, the airplane was above the ground before its descent.
Before the descent, airplane was at the height of 4,000 feet.
And the distance above the ground is represented by the positive integers and distance below the ground is represented by the negative integers.
Since, 4,000 feet is the distance of airplane above the ground.
So, the airplane was +4,000 feet above the ground before its descent.
