Teams A, B, and C have to complete two projects A and B. The workload of project B is more than that of project A (1/4). The time required for teams A, B, and C to complete project A are respectively It is 20 days, 24 days, 30 days. First send team A to work on project A alone, and teams B and C to work on project B together; after a few days, team C and team A are transferred to work on project A together. These two projects were completed at the same time. So how many days did Team C and Team B work together?
甲、乙、丙三个队要完成A、B两项工程，B工程的工作量比A工程的工作量多(1/4)，甲、乙、丙三队单独完成A工程所需时间分别是20天、24天、30天．先派甲队独做A工程，乙、丙两队共同做B工程；经过几天后，又调丙队与甲队共同做A工程．这样两项工程同时完工．那么丙队与乙队合做了几天？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 + (1/4)</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">120 * (5/4)</gadget>
<output>150</output>

<gadget id="calculator">120 / 24</gadget>
<output>5</output>

<gadget id="calculator">120 + 150</gadget>
<output>270</output>

<gadget id="calculator">120 / 20</gadget>
<output>6</output>

<gadget id="calculator">120 / 30</gadget>
<output>4</output>

<gadget id="calculator">6 + 5 + 4</gadget>
<output>15</output>

<gadget id="calculator">270 / 15</gadget>
<output>18</output>

<gadget id="calculator">5 * 18</gadget>
<output>90</output>

<gadget id="calculator">150 - 90</gadget>
<output>60</output>

<gadget id="calculator">60 / 4</gadget>
<output>15</output>

<result>15</result>