72*2.07-1.8*3.6 =3.6x20x2.07-1.8x3.6=3.6x(41.4-1.8)=3.6x(40-0.4)=3.6x40-3.6x0.4=144-1.44=142.566.8*16.8+19.3*3.2=6.8x16.8+(16.8+2.5)*3.2=6.8x16.8+16.8x3.2+2.5x3.2=16.8x(6.8+3.2)+2.5x4x0.8=16.8x10+10x0...