There are five numbers 3, 4, 5, 6, and 7. If you add any two numbers among them, the probability that the sum is an even number is ((())/(())).
3、4、5、6、7五个数，将其中的任意两个数相加，和是偶数的可能性是((())/(()))．
<gadget id="calculator">3 + 7</gadget>
<output>10</output>

<gadget id="calculator">4 / 10</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>