A project can be completed by A alone in 63 days and then by B alone in 28 days. If A and B cooperate, it can be completed in 48 days. Now A will do it alone for 42 days, and then B will complete it alone, how many more days will it take?
某工程由甲单独做63天，再由乙单独做28天可完成．如果甲、乙合作，48天就可完成．现在甲先单独做42天，然后再由乙单独完成，那么还要多少天？
<gadget id="calculator">1 / 48</gadget>
<output>1/48 = around 0.020833</output>

<gadget id="calculator">63 - 28</gadget>
<output>35</output>

<gadget id="calculator">(1/48) * 28</gadget>
<output>7/12 = around 0.583333</output>

<gadget id="calculator">1 - (7/12)</gadget>
<output>5/12 = around 0.416667</output>

<gadget id="calculator">35 / (5/12)</gadget>
<output>84</output>

<gadget id="calculator">1 / 84</gadget>
<output>1/84 = around 0.011905</output>

<gadget id="calculator">(1/48) - (1/84)</gadget>
<output>1/112 = around 0.008929</output>

<gadget id="calculator">1 / (1/112)</gadget>
<output>112</output>

<gadget id="calculator">(1/84) * 42</gadget>
<output>1/2 = around 0.5</output>

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

<gadget id="calculator">112 * (1/2)</gadget>
<output>56</output>

<result>56</result>