Question 1082145
20 artisans can accomplish a job in 30 straight days,
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r, rate for one artisan working alone


{{{20r*30=1}}}
{{{r=1/600}}}




25 artisans were hired at the beginning and 10 resigned after 20 days. 
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Two sections of time:  20 days and d day

Amount of work done, 1 whole job:
{{{25*r*20+15*r*d=1}}}


{{{highlight(25(1/600)*20+15(1/600)*d=1)}}}
Simplify and solve for d, "How long will it take for the remaining artisans to finish."