A project alone takes 15 days to complete, and B alone takes 18 days to complete. If A does 5 days first, and B does the rest, how many days will it take to finish?
一项工程甲单独做要15天完成，乙单独做要18天完成．如果甲先做5天，剩下的由乙独做，还要多少天才能完成？
<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(1/15) * 5</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 - (1/3)</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">1 / 18</gadget>
<output>1/18 = around 0.055556</output>

<gadget id="calculator">(2/3) / (1/18)</gadget>
<output>12</output>

<result>12</result>