Mom took 50 yuan to buy stationery for Xiaohong. She first bought 15 exercise books at 1.5 yuan each, and then used the remaining money to buy 2.5 yuan a pen. How many more pens can she buy?
妈妈拿了50元钱为小红买文具，她先买了每本1.5元的练习本15本，再用剩下的钱买2.5元一支的钢笔，还可以买几支钢笔？
<gadget id="calculator">15 * 1.5</gadget>
<output>22.5</output>

<gadget id="calculator">50 - 22.5</gadget>
<output>27.5</output>

<gadget id="calculator">27.5 / 2.5</gadget>
<output>11</output>

<result>11</result>