Master Li makes 5 pairs of shoes per hour. How many pairs of shoes did he make from 8:00 am to 4:00 pm?
李师傅每小时做5双鞋，他上午8时开始做，到下午4时一共做了多少双鞋？
<gadget id="calculator">4 - 8</gadget>
<output>-4</output>

<gadget id="calculator">12 + (-4)</gadget>
<output>8</output>

<gadget id="calculator">8 * 5</gadget>
<output>40</output>

<result>40</result>