In the diagram below, we have MN is parallel to PQ. We also know that OM=9, OQ=6, and PN=25.
If triangle OPQ's side lengths are 2/3 of OMN, then PN can be split so that OP is 2/3 of ON.
Basically, OP is 2/3 of ON. Together, they make up 25 (PN).
Can you solve from here?