Ravi earns twice as much in January as in each of the other months. What part of his annual earnings he earns in that month?

Suppose Ravi earns Rs. N in each of the 11 months.
Then earning in January = Rs. 2 x N.
∴ Total annual income = (11 x N + 2 x N) = Rs. 13 x N
Part of total earning in January = (2 x N) / (13 x N) = 2/13