Because cd is parallel to ab and the angle aob is opposite to the angle cod, the cod of triangle is like aob of triangle.

Get cd/ab= od/ob.

cd/ab+ 1=od/ob+ 1

(cd+ab)/ab=(od+ob)/ob

(cd+ab)/ab=bd/ob

(8+6)/8= 15/ob

ob= 15*8/ 14=60/7

od= 15-ob=45/7