18.9×2.7-89×0.27=18.9×2.7-8.9×2.7=（18.9-8.9）×2.7=10×2.7=27
18.9×2.7-89×0.27
=18.9×2.7-8.9×2.7........................积淀小数点与因数的小数点的关系，找因数2.7
=2.7×（18.9-8.9）....................乘法的分配律
=2.7×10
=27
