999×778+333×666 = 999×778+333× 3 ×222 = 999×778+999 ×222 = 999×（778+222 ） =999 × 1000 = 99900020.09×37-200.9×1.9+2009×0.82 = 20.09×37-20.09×10×1.9+20.09×100×0.82= 20.09 × (37 -19 +...我都会了就在这一瞬间