The escalator moves from bottom to top at a constant speed. Two impatient children think the escalator is slow, so on the moving escalator, the boy goes up one step per second, and the girl goes up two steps every three seconds. As a result, the boy took 50 seconds to reach the upstairs, and the girl took 60 seconds to reach the upstairs. How many steps does the escalator have?
自动扶梯以匀速由下往上行驶，两个性急的孩子嫌扶梯走得慢，于是在行驶的扶梯上，男孩每秒钟向上走1梯级，女孩每3秒钟走2梯级．结果男孩用50秒到达楼上，女孩用60秒到达楼上．该扶梯共有多少级？
<gadget id="calculator">1 * 50</gadget>
<output>50</output>

<gadget id="calculator">60 / 3</gadget>
<output>20</output>

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

<gadget id="calculator">50 - 40</gadget>
<output>10</output>

<gadget id="calculator">60 - 50</gadget>
<output>10</output>

<gadget id="calculator">10 / 10</gadget>
<output>1</output>

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

<gadget id="calculator">2 * 50</gadget>
<output>100</output>

<result>100</result>