By definition, skew lines are a pair of lines that are not parallel but do not intersect each other either. Hence, the conclusion would be, the lines are non-coplanar. An example would two random lines drawn in the x and y axes in a cartesian plane, respectively.
Skew lines are noncoplanar and do not intersect. Line a lies in plane Q and line b lies in plane R, so the lines are not coplanar. No other plane can be drawn through the lines, so they are not parallel. So, a and b are skew.
