There are two identical warehouses, and it takes A 6 hours, B 7 hours, and C 14 hours to move the goods from one warehouse. At the same time, A and B start to move the goods in a warehouse respectively. At the beginning, C first helped A to carry, and then went to help B to carry, and finally the goods in the two warehouses were moved at the same time. how many hours
有两个同样的仓库，搬运完一个仓库的货物，甲需6小时，乙需7小时，丙需14小时．甲、乙同时开始各搬运一个仓库的货物．开始时丙先帮甲搬运，后来又去帮乙搬运，最后两个仓库的货物同时搬完．则丙帮甲多少小时
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">1 / 14</gadget>
<output>1/14 = around 0.071429</output>

<gadget id="calculator">(1/6) + (1/7) + (1/14)</gadget>
<output>8/21 = around 0.380952</output>

<gadget id="calculator">2 / (8/21)</gadget>
<output>21/4 = around 5.25</output>

<gadget id="calculator">(1/6) * (21/4)</gadget>
<output>7/8 = around 0.875</output>

<gadget id="calculator">1 - (7/8)</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">(1/8) / (1/14)</gadget>
<output>7/4 = around 1.75</output>

<result>7/4 = around 1.75</result>