0.264×519+264×0.481=0.264*(519+481)=0.264*1000=264
0.264×519+264×0.481=0.264×519+0.264×1000×0.481=0.264×519+0.264×(1000×0.481)=0.264×519+0.264×481=0.264×(519+481)=0.264×1000=264