The students planted trees, and the number of willows planted was 20 less than three times that of fir trees. 190 willows were planted, how many fir trees were planted? How many.
同学们植树，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？多少．
<gadget id="calculator">190 + 20</gadget>
<output>210</output>

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

<result>70</result>