To process a batch of parts, it takes 75 hours for A to do it alone, and 50 hours for B to do it alone. It is known that B makes 12 more pieces than A per hour. If A's work efficiency is increased (1/2), and B makes 8 more pieces per hour than before, how many hours will it take for the two to work together to make two-thirds of the batch of parts?
加工一批零件，甲独做需75小时，乙独做需50小时，已知每小时乙比甲多做12件．如果甲的工效提高(1/2)，而乙每小时比原来多做8件，那么两人合做这批零件的三分之二需要多少小时？
<gadget id="calculator">1 / 50</gadget>
<output>1/50 = around 0.02</output>

<gadget id="calculator">1 / 75</gadget>
<output>1/75 = around 0.013333</output>

<gadget id="calculator">(1/50) - (1/75)</gadget>
<output>1/150 = around 0.006667</output>

<gadget id="calculator">12 / (1/150)</gadget>
<output>1_800</output>

<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">1_800 / 75</gadget>
<output>24</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

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

<gadget id="calculator">24 * (3/2)</gadget>
<output>36</output>

<gadget id="calculator">1_800 / 50</gadget>
<output>36</output>

<gadget id="calculator">36 + 8</gadget>
<output>44</output>

<gadget id="calculator">36 + 44</gadget>
<output>80</output>

<gadget id="calculator">(2/3) / 80</gadget>
<output>1/120 = around 0.008333</output>

<gadget id="calculator">1_800 * (1/120)</gadget>
<output>15</output>

<result>15</result>