Obviously bought 3 pens with 10 yuan, and got 1.9 yuan back. How much is each pen?
明明用10元钱买了3支钢笔，找回1.9元．每支钢笔多少钱？
<gadget id="calculator">10 - 1.9</gadget>
<output>8.1</output>

<gadget id="calculator">8.1 / 3</gadget>
<output>2.7</output>

<result>2.7</result>