Li Jun went to a stationery store to buy stationery. If he bought all the notebooks, he could buy 10 books. If he bought all the pencils, he could buy 15. Now he bought 4 notebooks first, how many pencils can he buy with the remaining money?
李军去文具店买文具，所带的钱如果全部买笔记本，刚好可以买10本，如果全部买铅笔，刚好可以买15枝．现在他先买了4本笔记本，剩下的钱还能买多少枝铅笔？
<gadget id="calculator">15 / 10</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">10 - 4</gadget>
<output>6</output>

<gadget id="calculator">(3/2) * 6</gadget>
<output>9</output>

<result>9</result>