The number of A is 6400, which is 400 more than the number of B. What is the sum of the two numbers of A and B?
甲数是6400，比乙数多400，甲乙两数的和是多少．
<gadget id="calculator">6_400 - 400</gadget>
<output>6_000</output>

<gadget id="calculator">6_000 + 6_400</gadget>
<output>12_400</output>

<result>12_400</result>