If the number of A is 30 more than the number of B, then how much is the number of A greater than the average of the two numbers of A and B
如果甲数比乙数多30，那么甲数比甲、乙两数的平均数多多少
<gadget id="calculator">30 - 15</gadget>
<output>15</output>

<result>15</result>