The Spring Festival is coming, and a supermarket bought 280 small Chinese knots, 20 less than three times the large Chinese knots purchased. How many large Chinese knots did the supermarket buy? (column equation solution)
春节快到了，某超市购进280只小中国结，比购进的大中国结的3倍少20只，超市购进多少只大中国结？(列方程解答)
<gadget id="calculator">280 + 20</gadget>
<output>300</output>

<gadget id="calculator">300 / 3</gadget>
<output>100</output>

<result>100</result>