The escalator in the shopping mall moves from bottom to top at a constant speed. Two children walk up and down the escalator. The girl walks from bottom to top, and the boy goes from top to bottom. As a result, the girl walks 40 steps to the upper floor, and the boy leaves. 80 steps to the downstairs, if the number of escalator steps that the boy walks per unit time is twice that of the girl, how many steps can be seen when the escalator is at rest?
商场的自动扶梯以匀速由下往上行驶，两个孩子在行驶的扶梯上上下走动，女孩由下往上走，男孩由上往下走，结果女孩走了40级到达楼上，男孩走了80级到达楼下，如果男孩单位时间内走的扶梯级数是女孩的2倍，则当该扶梯静止时，可看到的扶梯梯级有多少级？
<gadget id="calculator">80 - 40</gadget>
<output>40</output>

<gadget id="calculator">1 + 1</gadget>
<output>2</output>

<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<gadget id="calculator">20 + 40</gadget>
<output>60</output>

<result>60</result>