If the average of the numbers A and B is 49.5, and A's number is 59, what is the number of B?
如果甲、乙两数的平均数是49.5，甲数是59，那么乙数是多少．
<gadget id="calculator">49.5 * 2</gadget>
<output>99</output>

<gadget id="calculator">99 - 59</gadget>
<output>40</output>

<result>40</result>