The school bought 89 balls, 25 of which were basketballs, 37 were volleyballs, and the rest were leather balls. How many balls are there?
学校买来89个球，其中25个是篮球，37个是排球，剩下的是皮球．皮球有多少个？
<gadget id="calculator">89 - 25 - 37</gadget>
<output>27</output>

<result>27</result>