It takes 10 minutes for Xiao Ming to run from home to the park and back. If it takes 15 minutes to walk when going, and 15 minutes to run when returning, how many minutes does it take for Xiao Ming to walk back and forth?
小明从家到公园跑步去和回要10分钟，如果去时步行，回时跑步一共需要15分钟，那么小明来回都是步行要多少分钟．
<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">15 - 5</gadget>
<output>10</output>

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

<result>20</result>