If A and B work together to complete a project in 48 days, if A does it alone in 63 days, and B alone does it in 28 days, how many days will it take for B to complete it after A alone does it in 42 days?
一项工程，甲、乙合做48天完成，如果甲独做63天后，乙再独做28天完成，现由甲独做42天后，乙还要做多少天才完成？
<gadget id="calculator">1 / 48</gadget>
<output>1/48 = around 0.020833</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">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) - (1/84)</gadget>
<output>1/112 = around 0.008929</output>

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

<result>56</result>