A is twice as good a workman as B and together they finish a piece of work in 14 days. A alone can finish the work in?

(A's 1 day's work) : (B's 1 day's work) = 2 : 1
Now, ∵ (A + B)'s day's work = 1/14
⇒ A's 1 day's work = (1/14) x 2/3 = 1/21
∴ A alone can finish the work in 21 days.
[Dividing 1/14 in the ratio 2 : 1 ]