18. (3 points) A construction team is building a railway tunnel. When they completed $\frac{1}{3}$ of the task, the team adopted new equipment, which increased the construction speed by $20\%$. At the same time, to maintain the new equipment, the working hours per day were reduced to $\frac{4}{5}$ of the original. As a result, the entire project took 185 days to complete. From the above conditions, it can be deduced that, if the new equipment had not been adopted, the project would have taken $\qquad$ days to complete.
【Solution】Solution: Let the plan be to complete the task in $x$ days,
then the original work efficiency per day is $\frac{1}{x}$, and the improved work efficiency per day is $\frac{1}{x} \times (1+20\%) = \frac{1}{x} \times \frac{6}{5} = \frac{6}{5x}$. The time used to complete the project before the improvement is $\frac{x}{3}$ days, and the actual time used after improving the work efficiency is $\left(185 - \frac{x}{3}\right) \times \frac{4}{5}$ days. Therefore, $\frac{1}{3} + \left(185 - \frac{x}{3}\right) \times \frac{6}{5x} \times \frac{4}{5} = 1$,
$$
\begin{array}{l}
\frac{1}{3} + \left(185 - \frac{x}{3}\right) \times \frac{6}{5x} \times \frac{4}{5} - \frac{1}{3} = 1 - \frac{1}{3} \\
\left(185 - \frac{x}{3}\right) \times \frac{6}{5x} \times \frac{4}{5} = \frac{2}{3} \\
\left(185 - \frac{x}{3}\right) \times \frac{24}{25x} \div \frac{24}{25x} = \frac{2}{3} \div \frac{24}{25x}, \\
185 - \frac{x}{3} + \frac{x}{3} = \frac{25}{36}x + \frac{x}{3} \\
\frac{37}{36}x \div \frac{37}{36} = 185 \div \frac{37}{36} \\
x = 180
\end{array}
$$

Answer: The engineering team originally planned to complete the task in 180 days.
The answer is: 180.