A can do a piece of work in 12 days and B in 18 days. They begin together, but A leaves 2 days before the work is completed. In how many days is the work finished?

1. Let total time be T. B works all T days; A works (T − 2) days. 2. (T − 2)/12 + T/18 = 1. Multiply by 36: 3(T − 2) + 2T = 36. 3. 3T − 6 + 2T = 36 ⇒ 5T = 42 ⇒ T = **42/5 days** (8.4 days). _Source: IBPS RRB Officer Scale I Prelims PYQ (Examrace), Q.69_