The average of the two numbers of A and B is 42.5, A's number is 40, what is the number of B.
甲乙两个数的平均数是42.5，甲数是40，乙数是多少．
<gadget id="calculator">42.5 * 2</gadget>
<output>85</output>

<gadget id="calculator">85 - 40</gadget>
<output>45</output>

<result>45</result>