An escalator is moving upwards at a constant speed. A boy and a girl are walking up the escalator at the same time. The speed of the boy is twice the speed of the girl. It is known that the boy took 27 steps to reach the top, and the girl took 18 steps to reach the top, so when the escalator is stationary, how many steps can be seen from the escalator?
自动扶梯匀速向上行驶，一男孩与一女孩同时从自动扶梯向上走，男孩的速度是女孩速度的2倍．已知男孩走了27级到达顶部，而女孩走了18级到达顶部，那么当自动扶梯静止时，自动扶梯能看到的部分有多少级．
<gadget id="calculator">27 - 18</gadget>
<output>9</output>

<gadget id="calculator">18 * 2</gadget>
<output>36</output>

<gadget id="calculator">27 / 36</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">1 - (3/4)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">9 / (1/4)</gadget>
<output>36</output>

<gadget id="calculator">36 + 18</gadget>
<output>54</output>

<result>54</result>