7.5×0.8 +1.2x12.5+ 2.5x1.6
=2.5x3x0.8+1.2x2.5x5+2.5x1.6
=2.5x(3x0.8+1.2x5+1.6)
=2.5x(2.4+6+1.6)
=2.5x10
=25
7.5×0.8+1.2x12.5+2.5x1.6
=2.5×3×0.8+1.2x5×2.5+2.5x1.6
=2.5×2.4+6×2.5+2.5x1.6
=2.5×（2.4+6+1.6）
=2.5×10
=25
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