1, analysis: this question asks the distance that the puppy runs, because the speed of the puppy is known as 10km/h, and according to the distance = speed x time, only the time that the puppy runs is needed. The running time of the puppy is equal to the meeting time when Xiaoming and Xiaogang walk in opposite directions from A and B which are 26km apart: 26/(6+7)=2h. So the dog ran away 10X2=20km.

The key to this problem is to find the equivalence relation: the time when the puppy runs = the time when Xiao Ming and Xiao Gang meet.

2 Solution: If the original height of the candle is Xcm, the height of the first candle is (X- 16 )cm and the height of the second candle is (X- 12 )cm after 2 hours.

(X-2x6)/ (X-2x8)= 1.5 is used to formulate equations.

The solution is X=24cm.

Answer: The original height of two candles was 24cm.