4.2x7.8+2.2x42=4.2x7.8+2.2x4.2×10=4.2x7.8+4.2×22=4.2×(7.8+22)=4.2×29.8=4.2×(30-0.2)=4.2×30-4.2×0.2=126-0.84=125.16
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4.2×7.8+2.2×42=4.2×7.8+4.2×22=4.2×(7.8+22)=4.2×29.8=4.2×(30-0.2)=4.2×30-4.2×0.2=126-0.74=125.26