Let (A + C) complete the work in ‘a’days. So B will complete the work in 3 a days. $1/a+1/{3a}=1/10⇒3a=40⇒a=40/3$ Let (A + B) complete the work in n days. So C will complete the work in 2n days. $1/n+1/{2n}=1/10⇒n=30/2=15$(A + B + C)'s 1 day's work$ =1/10$ $1/A+1/40+1/30=1/10$ ⇒$1/A={12-3-4}/{120}=5/{120}=1/24$Therefore, A will complete the work in 24 days.