There are 24 chairs with 4 legs and stools with 3 legs in the school art room. If the number of chair legs and the number of stool legs add up to 87, how many chairs are there?
学校美术室里有4条腿的椅子和3条腿的凳子共24张，如果椅子腿数和凳子腿数加起来共有87条，那么有多少张椅子．
<gadget id="calculator">3 * 24</gadget>
<output>72</output>

<gadget id="calculator">87 - 72</gadget>
<output>15</output>

<gadget id="calculator">4 - 3</gadget>
<output>1</output>

<gadget id="calculator">15 / 1</gadget>
<output>15</output>

<result>15</result>