Seven persons M, N, O, P, Q, R and S sit in a linear row

Solution

R sits second from an extreme end of the row. Three persons sit between R and Q. N sits immediate right of Q.R sits either second from the extreme left end or extreme right end.Q sits either fourth to the right or left of R.____ R ____ _____ ____ Q N ……. CASE 1.____ Q N ____ ____ R ____ ……. CASE 2.
P sits third to the right of O. P sits neither at the end of the row nor adjacent to N. M sits to the left of S. P sits second to the right of R and O sits immediate left of R. M sits immediate right of R. S sits immediate right of P.O R M P S Q N ……. CASE 1.Case 2 will get discarded .____ Q N ____ ____ R ____ ……. CASE 2.Final arrangement O R M P S Q N