Answer:
1. 8 - x
The answer is 8 - x because the plant is 8 inches tall total this week, and to get how many it grew you would subtract it's height last week from 8.
2. The other expression, x - 8, could show how much a plant wilted, if it did. If the height went down, subtracting 8 from x could show how much the plant wilted.
Explanation:
:-) hope this helps!