The unit price ratio of ballpoint pens and pencils is 4:3. The school bought 15 ballpoint pens and 16 pencils and spent a total of 54 yuan. What is the unit price of ballpoint pens?
圆珠笔和铅笔的单价比为4：3，学校买了15支圆珠笔和16支铅笔一共用去了54元，那么圆珠笔的单价是多少元．
<gadget id="calculator">16 / 4</gadget>
<output>4</output>

<gadget id="calculator">4 * 3</gadget>
<output>12</output>

<gadget id="calculator">15 + 12</gadget>
<output>27</output>

<gadget id="calculator">54 / 27</gadget>
<output>2</output>

<result>2</result>