The students participated in the tree planting activity, and the number of willow trees planted was 20 fewer than that of fir trees. 190 willows were planted, how many fir trees were planted? (Solution of column equation)
同学们参加植树活动，植的柳树的棵数比杉树的3倍少20棵．柳树植了190棵，杉树植了多少棵？(列方程解)
<gadget id="calculator">20 + 190</gadget>
<output>210</output>

<gadget id="calculator">210 / 3</gadget>
<output>70</output>

<result>70</result>