Final answer:
The height of Lisa's candle will be more than 6 inches until the candle has been burning for at least 20 hours.
Step-by-step explanation:
To find out how many hours the height of Lisa's candle will be more than 6 inches, we need to determine when the candle will have a height of exactly 6 inches. Since the candle loses 10% of its original height every hour, we can use this information to set up an equation: 8 - 0.1x = 6, where x is the number of hours. Now, let's solve for x:
8 - 0.1x = 6
0.1x = 2
x = 20
The height of Lisa's candle will be more than 6 inches until the candle has been burning for at least 20 hours.