A batch of watermelons is shipped from the fruit shop, sold in the morning (3/10) and sold in the afternoon (5/10). What fraction is left?
水果店运来一批西瓜，上午卖出(3/10)，下午卖出(5/10)．还剩下几分之几？
<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">5 / 10</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(3/10) + (1/2)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>