Answer:
See below.
Step-by-step explanation:
Time taken by (A+B) to finish the work = 12 days

Time Taken by (B+C) to finish the work = 15 days

Time taken by (C+A) to finish the work = 20 days

Therefore,2 ( A + B + C)'s 1 day's work-





Therefore, A, B and C together can finish the work in 10 days.
Now,
A's 1 day's work = (A+B+C)'s 1 day's work - (B+C)'s 1 day's work



- Hence,A alone can finish the work in 30 days.
B's 1 day's work = (A+B+C)'s 1 day's work - (A+C')s 1 day's work



- Hence,B alone can finish the work in 20 days.
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A. The weight of the things inside the box
He seems to really care about his numbers. Maybe he should become a math teacher. The kind you really hate though. lol