The grain store receives a new batch of rice, the first day sells this batch of rice (3/7), and the second day sells this batch of rice (2/7). How much of this batch of rice was sold in two days? What fraction of this batch of rice is left?
粮店新进回一批大米，第一天卖出这批大米的(3/7)，第二天卖出这批大米的(2/7)．两天一共卖出这批大米的几分之几？还剩下这批大米的几分之几？
<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">(3/7) + (2/7)</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">1 - (5/7)</gadget>
<output>2/7 = around 0.285714</output>

<result>2/7 = around 0.285714</result>