Xiao Ming's speed is 5 kilometers per hour empty-handed, and 3 kilometers per hour with a schoolbag. One day, when he arrived at school, he found that he didn't bring his schoolbag, so he went back to get it.
小明空手速度为5公里每小时，拿书包为3公里每小时，一天，他到达学校时发现书包没带，又回去拿，一来一往共用7小时，问小明家离学校的距离？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(2/5) + (1/3)</gadget>
<output>11/15 = around 0.733333</output>

<gadget id="calculator">7 / (11/15)</gadget>
<output>105/11 = around 9.545455</output>

<result>105/11 = around 9.545455</result>