Final answer:
Mitch and Terry are 0.5 kilometers away from the scenic cliff after descending 1.3 kilometers and ascending 0.8 kilometer back towards it.
Step-by-step explanation:
To find out how far Mitch and Terry are from the scenic cliff after climbing 0.8 kilometer back up, we need to calculate the net distance they are from the cliff after their descent and subsequent ascent. They initially climbed 6.6 kilometers to reach the cliff and then descended 1.3 kilometers, which leaves them 6.6 - 1.3 = 5.3 kilometers above their starting point. After climbing back up 0.8 kilometer, they are 5.3 + 0.8 = 6.1 kilometers above their starting point. Hence, considering they initially reached 6.6 kilometers, after the ascent, they are 6.6 - 6.1 = 0.5 kilometers away from the scenic cliff.