There are 8 rows of pine trees in the campus, with 7 trees in each row. 37 pine trees have been watered, how many have not been watered?
校园里有8排松树，每排7棵．37棵松树已经浇了水，还有多少棵没浇水？
<gadget id="calculator">7 * 8</gadget>
<output>56</output>

<gadget id="calculator">56 - 37</gadget>
<output>19</output>

<result>19</result>