Then 1.5 (x-2× 8) = x-2× 6.

The solution is x = 24.

So the original candle height is 24cm.

(2) Suppose this moment is y hours later. It takes 24 ÷ 8 = 3 hours for the first candle to burn out.

Then 2 (24-8y) = 24-6y (y < 3).

The solution is y = 2.4 < 3.

So it should be within 2.4 hours.