Calculation: 2.1+2.3+2.5+2.7+...+5.7+5.9.
计算：2.1+2.3+2.5+2.7+…+5.7+5.9．
<gadget id="calculator">2.1 + 5.9</gadget>
<output>8</output>

<gadget id="calculator">5.9 - 2.1</gadget>
<output>3.8</output>

<gadget id="calculator">3.8 / 0.2</gadget>
<output>19</output>

<gadget id="calculator">19 + 1</gadget>
<output>20</output>

<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">8 * 10</gadget>
<output>80</output>

<result>80</result>