解:(1)乘A型车费用=10+1.2×(20-3)=30.4元;乘B型车费用=8+1.4×(20-3)=31.8元.故从节省费用的角度,应乘坐A型车.(2)设乘A型车为x千米,费用为:10+1.2×(x-3)=1.2x+6.4(元)乘B型车费用:8+1.4×(x-3)=1.4x+3.8(元)乘A型车与乘B型车的价差y=1.2x+4.4-(1.4x+0.8)=-0.2x+2.6(元).