⒈书的价格:4+9+7=12元小萍带:12-4=6元小静带:12-9=1元⒉连接DE在△ABC中,∵D是AB的中点∴S△CDB=S△ACD=(1/2)S△ABC=(1/2)×24=12cm²∵BE=2EC∴CE=(1/3)BC∴S△ACE=(1/3)S△ABC=8cm²则S△AEB=16cm²在△AEB中,D是AB的中点∴S△AED=S△EDB=(1/2)S△AEB=8cm²∵F是CD的中点∴S△CFE=S△FED∵S△ACF=S△ACE-S△CFE=8-S△CFE且S△ACF=S△ACD-S△AFD=12-S△AFD∴8-S△CFE=12-S△AFD即:S△AFD-S△CFE=4又∵S△AFD+S△EFD=8且S△CFE=S△FED∴S△CFE=2cm²∴S阴=S△CDB-S△CFE=12-2=10cm²