If you buy 2 ballpoint pens and 4 fountain pens, you pay 15.4 yuan in total, and each ballpoint pen is 1.8 yuan. How much is each pen? (solution by equation)
买2支圆珠笔和4支钢笔共付15.4元，每支圆珠笔1.8元，每支钢笔多少元？(用方程解)
<gadget id="calculator">2 * 1.8</gadget>
<output>3.6</output>

<gadget id="calculator">15.4 - 3.6</gadget>
<output>11.8</output>

<gadget id="calculator">11.8 / 4</gadget>
<output>2.95</output>

<result>2.95</result>