Wang Hong's home is 12 kilometers away from the school. One day Wang Hong went to school, and when he arrived at school, he found that he had lost his Chinese books at home, and ran home to get them and then ran to school. How many kilometers did he walk in total?
王红家离学校12千米，一天王红上学，到校时发现语文书丢在家里，又跑回家拿再跑到学校，他一共走多少千米？
<gadget id="calculator">12 * 2</gadget>
<output>24</output>

<gadget id="calculator">12 + 24</gadget>
<output>36</output>

<result>36</result>