The correct answer is (A):
Let r and g be the rates of work of Ramesh and Ganesh respectively.
Let (r + g)16 = 1
⇒ (r+g) = 1/16
(r+g)7 = 7/16
Remaining work to be done = 9/16
Given, (0.7r+g)10 = 9/16
7r+10g = 9r+9g
g = 2r
r = 1/48
g = 1/24
Time taken by g alone to complete the work 9/16/1/24 = 13.5