The school bought back 24 basketballs. The number of basketballs bought back was three times that of volleyballs. The number of footballs bought back was 9 more than volleyballs. How many footballs did the school buy back?
学校买回24个篮球，买回的篮球的个数是排球的3倍，买回的足球比排球多9个，学校买回多少个足球？
<gadget id="calculator">24 / 3</gadget>
<output>8</output>

<gadget id="calculator">8 + 9</gadget>
<output>17</output>

<result>17</result>