The Spring Festival is coming, a supermarket bought 850 small Chinese knots, which is 50 less than three times the purchased big Chinese knots, how many big Chinese knots did the supermarket buy?
春节快到了，某超市购进850只小中国节，比购进的大中国结的3倍少50只，超市购进多少只大中国结？
<gadget id="calculator">850 + 50</gadget>
<output>900</output>

<gadget id="calculator">900 / 3</gadget>
<output>300</output>

<result>300</result>