The price of a fountain pen is three times that of a ballpoint pen. It is known that a ballpoint pen is 9 yuan cheaper than a fountain pen. How much is a fountain pen?
钢笔的价钱是圆珠笔的3倍，已知一支圆珠笔比一支钢笔便宜9元，一支钢笔多少钱？
<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<gadget id="calculator">9 / 2</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">(9/2) * 3</gadget>
<output>27/2 = around 13.5</output>

<result>27/2 = around 13.5</result>