Given: l∥m∥n,
In △OAC and △OBD,
∠AOC=∠DOB (Vertically opposite angles)
∠OCA=∠ODB (Alternate angles of parallel
lines)
∠OAC=∠OBD (Alternate angles of parallel
lines)
Thus, △OAC∼△OBD (AAA rule)
OAOB=OCOD
8OB=55
OB=8 cm
Similarly, △OEC∼△OFD (AAA rule)
OEOF=OCOD
10OF=55
OF=10 cm