Question 1013178
The problem tells you that during the 3rd minute, the candle burned 3/4 inch.
That means it was 1 1/2 inches taller than eight inches when it started, or 9 1/2 inches tall originally.  Assuming it burns at the same rate, it will take
9 1/2 / 3/4 = 12 2/3 minutes to burn out.