There is a batch of watermelons in the supermarket. After selling (5/8) tons, there are still (2/5) tons left. How many tons of watermelons are there?
超市里有一批西瓜，卖出(5/8)吨后，还剩(2/5)吨，原来有西瓜多少吨？
<gadget id="calculator">5 / 8</gadget>
<output>5/8 = around 0.625</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(5/8) + (2/5)</gadget>
<output>41/40 = around 1.025</output>

<result>41/40 = around 1.025</result>