ballpoint pen is 2.2 yuan, and an eraser is 0.9 yuan cheaper than a ballpoint pen. How much does it cost to buy an eraser and a ballpoint pen?
一支圆珠笔2.2元，一块橡皮比一支圆珠笔便宜0.9元钱．买一块橡皮和一支圆珠笔一共要多少元？
<gadget id="calculator">2.2 - 0.9</gadget>
<output>1.3</output>

<gadget id="calculator">1.3 + 2.2</gadget>
<output>3.5</output>

<result>3.5</result>