It takes 12 days and 1 day to complete a single maintenance112. Similarly, the repair of B 1 day 1/20 A/B * * takes 5 days to complete 5 * (112+65438. The working day of 3 years is workload/work efficiency = (1/3)/(112) = 4 days, and * * * is 5+4=9 days.

In fact, the idea is very simple, that is, it is more troublesome to express it clearly with words and formulas. If I write like this, you should understand. Formulas also have answers and best answers. Who will you give them to?