方法一:135x74=135x2x37=270x37=(200+70)x37=200x37+70x37=7400+2590=9990方法二:原式=135x(70+4)=135x70+135x4=9450+540=9990方法三:原式=135x(80-6)=135x80-135x6=10800-810=9990