The average age of the three numbers A, B, and C is 22 years old. If the average age of A, B, and B is 18, and the average age of B, C is 25, then how old is B?
甲乙丙三个数的平均年龄为22岁，如果甲乙的平均年龄是18岁，乙丙的平均年龄是25岁，那么乙的年龄是多少岁．
<gadget id="calculator">25 * 2</gadget>
<output>50</output>

<gadget id="calculator">18 * 2</gadget>
<output>36</output>

<gadget id="calculator">22 * 3</gadget>
<output>66</output>

<gadget id="calculator">50 - 66</gadget>
<output>-16</output>

<gadget id="calculator">36 + (-16)</gadget>
<output>20</output>

<gadget id="calculator">50 - 20</gadget>
<output>30</output>

<result>30</result>