Explanation:
that makes NOP and QRP similar triangles.
that means that there is one common scale factor for the lengths of all pairs of correlating sides.
that means
QR/NO = RP/OP
OP = OR + RP
20/32 = RP/(12 + RP)
20(12 + RP) = 32RP
240 + 20RP = 32RP
240 = 12RP
RP = 20