city decides that teams A, B, and C will jointly build two roads with equal road thickness and width. It is known that the second one is 1/4 longer than the first one. To build a road alone, it takes Team A 20 days, Team B 24 days, and Team C 30 days. After the two roads are started at the same time, Team B will build the first road alone, and Teams A and C will jointly build the second road. highway. After a period of time, team A was transferred to the first road construction site to jointly repair with team B. In this way, two roads were built at the same time. How long did Team A and Team C practice together?
某市决定由甲、乙、丙三个队共同修筑路面厚度、宽度都相等的两条公路．已知第二条比第一条长1/4．单独修一条公路，甲队要20天，乙队要24天，丙队要30天，两条路同时开工后，先由乙队单独修第一条公路，甲、丙两队合修第二条公路．一段时间后，又把甲队调往第一条公路工地，与乙队合修．这样两条公路同时修成．问甲队与丙队合修了多长时间？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

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

<gadget id="calculator">2 + (1/4)</gadget>
<output>9/4 = around 2.25</output>

<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">1 / 24</gadget>
<output>1/24 = around 0.041667</output>

<gadget id="calculator">(1/20) + (1/24) + (1/30)</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">(9/4) / (1/8)</gadget>
<output>18</output>

<gadget id="calculator">(1/30) * 18</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(1/4) - (3/5)</gadget>
<output>-7/20 = around -0.35</output>

<gadget id="calculator">1 + (-7/20)</gadget>
<output>13/20 = around 0.65</output>

<gadget id="calculator">(13/20) / (1/20)</gadget>
<output>13</output>

<result>13</result>