解：①當(dāng)?$0≤x≤60$?時(shí)，如圖所示
由?$GF//CD，$?得?$\frac {EF}{ED}=\frac {GF}{CD}，$?即?$\frac {y}{60-x+y}=\frac {1.6}{4.8}$?
∴?$y=-\frac 12x+30$?
②當(dāng)?$60$?
由?$GF//CD，$?得?$\frac {EF}{ED}=\frac {GF}{CD}，$?即?$\frac y{x-60+y}=\frac {1.6}{4.8}$?
∴?$y=\frac 12x-30$?
