There are 5 tons of coal, after burning (2/5) tons, and then burning (2/5) tons, what is the remaining mass of tons?
有5吨煤，烧了(2/5)后，又烧了(2/5)吨，还剩下的质量是多少吨
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">5 * (2/5)</gadget>
<output>2</output>

<gadget id="calculator">5 - 2 - (2/5)</gadget>
<output>13/5 = around 2.6</output>

<result>13/5 = around 2.6</result>