Examining the figure, we can determine that QR is a part of two separate planes, MQR and PQR.
By the definition of skew, we can rule out any line that runs along either of these planes.
ML * MR *
LQ * PQ *
NR * PN *
This leaves five potential skew lines left. Let's mark these on the diagram.
Since JK is coplanar with QR it cannot be skew to QR. Therefore, there are four lines that are skew to QR.
JN, KP, JM, KL
