Uncle Li rides a motorcycle to the county town to study, travels 42 kilometers per hour, and arrives in 3 hours. It only took 2 hours to return. How many kilometers per hour did Uncle Li travel when he returned?
李叔叔骑摩托车到县城去学习，每小时行驶42千米，3小时到达．返回时只用了2小时，李叔叔返回时每小时行多少千米？
<gadget id="calculator">3 / 2</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">42 * (3/2)</gadget>
<output>63</output>

<result>63</result>