The sum of the current ages of A, B, and C is 143 years old. When A's age is half of B's, C is 38 years old; when C's age is twice B's, A's 17 years old. So, how old is B now?
A、B、C现在的年龄和是143岁．当A的年龄是B的一半时，C是38岁；当C的年龄是B的2倍时，A是17岁．那么，B现在多少岁？
<gadget id="calculator">38 - 17</gadget>
<output>21</output>

<gadget id="calculator">2 - 1</gadget>
<output>1</output>

<gadget id="calculator">2 + 1</gadget>
<output>3</output>

<gadget id="calculator">21 / 3</gadget>
<output>7</output>

<gadget id="calculator">2 * 7</gadget>
<output>14</output>

<gadget id="calculator">7 + 14 + 38</gadget>
<output>59</output>

<gadget id="calculator">143 - 59</gadget>
<output>84</output>

<gadget id="calculator">84 / 3</gadget>
<output>28</output>

<gadget id="calculator">14 + 28</gadget>
<output>42</output>

<result>42</result>