It takes Xiao Yingtong 20 minutes to ride a bicycle from home to Yale to study, and 40 minutes if she rides a bicycle when she goes there and walks back. How many minutes does it take Xiaoying to walk back and forth.
小英彤从家到雅乐读书，如果往返都骑自行车需要20分钟，如果去时骑车，回来步行，那么一共用40分钟．小英步行来回需要多少分钟．
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">40 - 10</gadget>
<output>30</output>

<gadget id="calculator">30 * 2</gadget>
<output>60</output>

<result>60</result>