Final answer:
David's elevation after climbing 200 meters is 900 meters. If he had descended 300 meters, his elevation would be 400 meters.
Step-by-step explanation:
To find David's elevation after climbing 200 meters, we need to add 200 to his starting elevation of 700 meters.
Count wise : 200 + 700 that equals 900.
This gives us an elevation of 900 meters.
If David had descended 300 meters instead, we need to subtract 300 from his starting elevation of 700 meters.
Count wise : 700 - 300 that equals 400.
This gives us an elevation of 400 meters.