For a project, A and B cooperate to complete in 20 days, and B and C cooperate in 30 days to complete. In fact, A worked for 3 days first, then C worked for 4 days, and finally B completed the remaining tasks. It is known that the amount of work completed by A is 1.5 times that of C. Ask: How many days did B actually work?
一项工程，甲乙合作要20天完成，乙丙合作要30天完成．实际上，甲先干了3天，丙接着干了4天，最后由乙完成了余下的任务．已知甲完成的工作量是丙的1.5倍，问：乙实际上工作了多少天？
<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/20) - (1/30)</gadget>
<output>1/60 = around 0.016667</output>

<gadget id="calculator">4 / 3</gadget>
<output>4/3 = around 1.333333</output>

<gadget id="calculator">1.5 * (4/3)</gadget>
<output>2</output>

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

<gadget id="calculator">(1/60) / 1</gadget>
<output>1/60 = around 0.016667</output>

<gadget id="calculator">(1/30) - (1/60)</gadget>
<output>1/60 = around 0.016667</output>

<gadget id="calculator">(1/60) * 3</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/60) * 4</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">1 - (1/20) - (1/20) - (1/15)</gadget>
<output>5/6 = around 0.833333</output>

<gadget id="calculator">(5/6) / (1/60)</gadget>
<output>50</output>

<result>50</result>