text: alg. 2 math help?? eek!? a mechanical sorter can process a bag of mail in 18 minutes. after the sorter has been working for a time, it breaks down. the rest of the mail it was sorting is divided equally between two older machines, each of which would take 60 minutes to complete the job working alone. the mail is finished being sorted 20 minutes after the first machine started working. how long did the first machine work before breaking down??  work too please. thank you very much. appreciate it. :] n/r1 = 18 n/r2 = 60 18r1 = 60r2 r2 = 18r1/60 (n-n)/2r2 + n/r1 = 20 60(n - n)/36r1 + n/r1 = 20 (60/36)(n/r1) - (60/36)(n/r1) + n/r1 = 20 (60/36)(18) + n/r1(1 - (60/36)) = 20 t = (20 - (60/36)(18))/(1 - (60/36)) t = (20*36 - 60*18)/(36 - 60) t = (720 - 1080)/-24 t = 360/24 t = 15 min