脱式计算 （能用简便方法的简便计算）
①2.07÷2.5÷0.4                ②21.36÷0.8﹣12.9
③0.125×32×2.5                ④0.65×201
⑤1.2×2.5+8×0.25              ⑥50.4×19+50.4．