The average of the numbers A and B is 54, the number of A is 4 more than the number of B, what is the number of B?
甲、乙两数的平均数是54，甲数比乙数多4，乙数是多少．
<gadget id="calculator">54 * 2</gadget>
<output>108</output>

<gadget id="calculator">108 - 4</gadget>
<output>104</output>

<gadget id="calculator">104 / 2</gadget>
<output>52</output>

<result>52</result>