∵四边形ABCD是平行四边形∴OA=OC,OB=OD,AD=BC=6cm∵△ABO的周长=AB+OA+OB =8+OA+OB∴OA+OB=18-8=10即OA+OD=10∴△AOD的周长=AD+OA+OD =6+10 ...谢啦