Uncle Li bought 23 boxes of drinks online for 643 yuan. If you buy it from a shopping mall, it costs 31 yuan a box. How much money did Uncle Li spend less?
李叔叔从网上用643元购买了23箱饮料．如果从商场里买，一箱要花31元，李叔叔一共少花了多少钱？
<gadget id="calculator">31 * 23</gadget>
<output>713</output>

<gadget id="calculator">713 - 643</gadget>
<output>70</output>

<result>70</result>