这几道题的简便算法以及得数
456-299,456+109,456-109,23+45+55+77,891-238-562,571-（271-48）,56.5-41.2+43.5-58.8,25×125×5×2×4×8,25×1.6,125×72,47×56+44×47,99×45,101×45,9.9×45+4.5,101×45-45,56×11 37×12+12×56+12×7,75×21+25×37,120×（1/2+1/3+1/4）,25×1/3×3/5×3/10,2007×2005/2006,