Let the work done by B be x.
∴Work done by A =2x
Work done by A and B together in 14 days =1
Work done by A and B together in 1 day =114
⇒ Work done by A in 1 day + Work done by B in 1 day =114
x+2x=114
⇒3x=114
⇒x=142
Work done by B in 1 day =142
∴ Work done by A in 1 day =121
Hence, to finish the work, A require 21 days.
Hence, A alone can finish the work in 21 days.