A project can be completed by A alone for 63 days, and then by B alone in 28 days. If A and B work together, it takes 48 days to complete. Now A works alone for 42 days, and then B continues. Days can be done?
某工程由甲单独做63天，再由乙单独接着做28天可以完成，如果甲、乙两人合作需48天完成，现在甲先单独做42天，然后再由乙接着做，还需多少天可以完成？
<gadget id="calculator">28 / 48</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">63 - 28</gadget>
<output>35</output>

<gadget id="calculator">(5/12) / 35</gadget>
<output>1/84 = around 0.011905</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">1 / 48</gadget>
<output>1/48 = around 0.020833</output>

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

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

<result>56</result>