There are 46 poplars and willows in the woods. There are 4 rows of poplars and 9 trees in each row. How many willows are there?
树林里有杨树和柳树共46棵，其中杨树有4行，每行9棵，求柳树有几棵．
<gadget id="calculator">4 * 9</gadget>
<output>36</output>

<gadget id="calculator">46 - 36</gadget>
<output>10</output>

<result>10</result>