A bottle of 5 liters of peanut oil is used for the first time (3/10), and the second time (1/5), what fraction of the oil is left in the bottle?
一瓶5升的花生油，第一次用去它的(3/10)，第二次用去(1/5)，还剩这瓶油的几分之几？
<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (3/10) - (1/5)</gadget>
<output>1/2 = around 0.5</output>

<result>1/2 = around 0.5</result>