A is older than B (1/6), C is younger than A (1/3), B is 4 years older than C, how old is B?
甲的年龄比乙的年龄多(1/6)，丙的年龄比甲的年龄少(1/3)，乙比丙大4岁，求乙的年龄是多少岁？
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 + (1/6)</gadget>
<output>7/6 = around 1.166667</output>

<gadget id="calculator">1 / (7/6)</gadget>
<output>6/7 = around 0.857143</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 - (1/3)</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">(6/7) - (2/3)</gadget>
<output>4/21 = around 0.190476</output>

<gadget id="calculator">4 / (4/21) / (7/6)</gadget>
<output>18</output>

<result>18</result>