A piece of iron wire, its (1/5) is used for the first time, and its (1/2) is used for the second time, what fraction of the total length is left?
一根铁丝，第一次用去它的(1/5)，第二次用去它的(1/2)，还剩下全长的几分之几？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 - (1/5) - (1/2)</gadget>
<output>3/10 = around 0.3</output>

<result>3/10 = around 0.3</result>