In the subway station, there is an upward escalator from the platform to the ground. When Xiaoqiang takes the escalator, if he steps up one step per second, then he walks through 20 steps and reaches the ground. If he steps up two steps per second , then after walking through 30 steps, reach the ground level and then reach the ground. How many steps are there from the platform to the ground?
在地铁车站中，从站台到地面有一架向上的自动扶梯，小强乘坐扶梯时，如果每秒向上迈一级台阶，那么他走过20级台阶后到达地面，如果他每秒向上迈两级台阶，那么走过30级台阶后到达地面级台阶后到达地面．问从站台到地面有多少级台阶？
<gadget id="calculator">30 / 2</gadget>
<output>15</output>

<gadget id="calculator">20 / 1</gadget>
<output>20</output>

<gadget id="calculator">30 - 20</gadget>
<output>10</output>

<gadget id="calculator">20 - 15</gadget>
<output>5</output>

<gadget id="calculator">10 / 5</gadget>
<output>2</output>

<gadget id="calculator">15 * 2</gadget>
<output>30</output>

<gadget id="calculator">30 + 30</gadget>
<output>60</output>

<result>60</result>