The escalator travels upwards at a uniform speed. A boy and a girl walk up the escalator at the same time. The speed of the boy is twice that of the girl. It is known that the boy has taken 27 steps to reach the top of the escalator, and the girl has taken 18 steps to reach the top. ． How many steps are there in the exposed part of the escalator?
自动扶梯以均匀的速度向上行驶，一男孩与一女孩同时从自动扶梯向上走，男孩的速度是女孩的2倍，已知男孩走了27级到达扶梯的顶部，而女孩走了18级到达顶部．问扶梯露在外面的部分有多少级？
<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>