Li Ming went to the city to buy school supplies on Sunday. If he bought all the exercise books, he could buy 10 books; if he bought all the pencils, he could buy 15 sticks. Li Ming bought 4 exercise books first, and how many pencils can be bought with the remaining money.
李明星期天进城买学习用品，所带的钱如果全部买练习本，可以买10本；如果全部买铅笔，可以买15枝．李明先买了4本练习本，剩下的钱还可以买多少枝铅笔．
<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>