How many persons are sitting between O and N when counted from the left of O?

We have, R sits second to the left of P.   Only two persons are sitting between P and N. From the above condition, there are two possibilities. Again we have,  Only one person sits between N and M.  M does not sit adjacent to P.  The number of persons sits between P and M is the same as the number of persons sit between P and Q. Again we have, The number of persons sits between R and N is one less than the number of persons sits between Q and M, when counted to the right of both R and M respectively M sits exactly in the middle of L and N.  sits second to the right of L. From the above condition, case1 gets eliminated. Case 2 shows the final arrangement.