Question

Lines p, q are coplanar. So are the lines p, r. Can we conclude that the lines p, q, r are coplanar?

Answer 1

No p, q and r are not necessarily coplanar .
e.g.:-If we take p as intersecting line of two consecutive walls of a room , q as a line on the first wall and r on the second wall whose(both walls) intersection is line p .
Then we can see that p , q and r are not coplanar.