41.2×8.1＋11×1.25＋53.7×1.9=41.2×(10-1.9)+53.7×1.9+11×1.25=412+12.5×1.9+1.1×12.5=412+12.5×(1.1+1.9)=412+12.5X3=449.5
41.2×8.1＋11×1.25+41.2×1.9+12.5×1.9=41.2×(8.1+1.9)+11×1.25+12.5×1.9412+11×1.25+1.25×19=412+1.25×30=412+37.5=449.5
原式=（53.7-12.5）x8.1＋11×1.25＋53.7×1.9 =53.7x(8.1+1.9)+(11-81)x1.25 =537-70x1.25 =449.5
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