8. (6 points) A roll of wire, the first time used half of the total length plus 3 meters, the second time used half of the remaining minus 10 meters, the third time used 15 meters, and finally 7 meters were left. How long was the roll of wire originally?
【Solution】Solve: $[(15+7-10) \times 2+3] \times 2$
$$
\begin{array}{l}
=[12 \times 2+3] \times 2 \\
=[24+3] \times 2 \\
=27 \times 2 \\
=54 \text { (meters) }
\end{array}
$$

Answer: The original length of this roll of wire is 54 meters.