The school bought back 12 pens and some schoolbags for a total of 188.7 yuan. Each pen is 2.6 yuan, and each schoolbag is 10.5 yuan. How many schoolbags did the school buy back?
学校买回12枝钢笔和一些书包，共用去188.7元．每枝钢笔2.6元，每个书包10.5元．学校买回多少个书包？
<gadget id="calculator">2.6 * 12</gadget>
<output>31.2</output>

<gadget id="calculator">188.7 - 31.2</gadget>
<output>157.5</output>

<gadget id="calculator">157.5 / 10.5</gadget>
<output>15</output>

<result>15</result>