Problem: abel can complete a work in 8 days , ben in 12 days and carla in 15 days . all of them began the work together , but abel had to leave after 2 days and ben 3 days before the completion of the work . how long did the work last ?
Rationale: "abel in the 2 days that he worked completed 1 / 4 of the job = 3 / 4 remains then if ben had to leave 3 days before the completion , this means that carla had to work alone for these 3 days in which she completed 1 / 5 of the job . now together , ben and carla completed the job in ( 1 / 12 + 1 / 15 ) ( t ) = 3 / 20 3 / 20 ( t ) = 3 / 20 - - - > t = 1 therefore , these 1 day worked plus the 3 days that carla had to work by herself add to 4 days answer : a"
annotated_formula: multiply(add(2, 3), 3)