A and B finish the job in 15 days.while A,B and C can finish it in 12 days . C alone will finish the job in
Choose the most appropriate option:  A) 40 days  B) 30 days  C) 60 days  D) 70 days  E) 50 days

Rationale: "explanation : 12 = ( 15 * x ) / ( 15 + x ) 180 + 12 x = 15 x 3 x = 180 x = 60 answer : option c"
Answer: C