The final answer would be 3.5 inches tall or if you need fractions it would be 3 and 1/2. Here’s the explanation: the candle is originally eight inches tall and for every hour it burns it loses 3/4 of an inch which is .75. It will be burning till 11:00 at night which means it will be burning for six hours. All you need to do is multiply how much of the candle is burned every hour (.75) by how many hours. This will give you 4.5 inches burned by 11:00. But the question asked for how tall the candle will be, so you simply just subtract how much of the candle will have burned(4.5 inches) by the height (8 inches) and you get 3.5 inches.
