3.7×2.1+37×0.79＝3.7×2.1+3.7×7.9＝3.7×（2.1+7.9）＝3.7×10＝37
3.7×2.1+37×0.79=37×0.21+37×0.79=37（0.21+0.79）=37×1=37.
