Xiaofang went to the stationery store to buy 5 exercise books and 4 pens, and the total cost was 4.25 yuan. It is known that each exercise book is 0.45 yuan, how much is each pen? (column equation solution)
小芳到文具店买5本练习本和4枝笔，共用去4.25元，已知练习本每个0.45元，笔每只多少元？(列方程解答)
<gadget id="calculator">0.45 * 5</gadget>
<output>2.25</output>

<gadget id="calculator">4.25 - 2.25</gadget>
<output>2</output>

<gadget id="calculator">2 / 4</gadget>
<output>1/2 = around 0.5</output>

<result>1/2 = around 0.5</result>