Xiao Ming wants to buy some stationery with 100 yuan. He first bought 9 notebooks for 45 yuan, and plans to use the rest of the money to buy pens, each pen is 2.5 yuan. How many pens can Xiao Ming buy?
小明要用100元买一些文具，他先花45元买了9本笔记本，并准备用剩下的钱买钢笔，每支钢笔2.5元．小明可以买几支钢笔？
<gadget id="calculator">100 - 45</gadget>
<output>55</output>

<gadget id="calculator">55 / 2.5</gadget>
<output>22</output>

<result>22</result>