A job alone takes 4 hours, and B alone takes 8 hours to complete. Now after A has done it for a certain number of hours, B will continue to do it, a total of 5 hours to complete. How many hours did A do it?
一件工作，甲单独做要4小时，乙单独做要8小时完成，现在甲做了若干小时后，乙接着做，共5小时完成．甲做了几小时？
<gadget id="calculator">1 / 8</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">(1/8) * 5</gadget>
<output>5/8 = around 0.625</output>

<gadget id="calculator">1 - (5/8)</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(3/8) / (1/4)</gadget>
<output>3/2 = around 1.5</output>

<result>3/2 = around 1.5</result>