From the first sentence we can say that there are 15 people between Ram and Sunil and Ram has 17 people to his right.
Jack is 4th to right pf Sunil, so he must have 3 people between him and Sunil. Since there are 15 people between Sunil and Ram, we can say that there will be 15−4=11 people between Jack and Ram. Jack is 11th from left and he also has Sunil to his left. Jack will have 10 people to his left and Sunil is 4 th to his left, This must mean that Sunil will have 10−4=6 people to his left.