The escalator goes from bottom to top, Xiao Ming walks 100 steps from top to bottom, and Xiao Hong walks 50 steps to the top from bottom to top. It is known that Xiao Ming’s walking speed is three times that of Xiao Hong’s. How many steps are there from bottom to top when the escalator is at rest? ?
自动扶梯由下向上，小明由上向下走了100级到底，小红由下向上走了50级到顶，已知小明步行速度是小红的3倍，问扶梯静止时由底到顶共几级？
<gadget id="calculator">100 - 50</gadget>
<output>50</output>

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

<gadget id="calculator">2 + 3</gadget>
<output>5</output>

<gadget id="calculator">50 / 5</gadget>
<output>10</output>

<gadget id="calculator">10 * 2</gadget>
<output>20</output>

<gadget id="calculator">100 - 20</gadget>
<output>80</output>

<result>80</result>