7.8×3.04+5.96×7.8+7.8
=7.8×（3.04+5.96+1）
=7.8×10
=78
0.9999×0.9+0.1111×1.9
=0.1111×8.1+0.1111×1.9
=0.1111×（8.1+1.9）
=0.1111×10
=1.111
86.4÷6.4-0.4
=86.4÷1.6÷4-0.4
=54÷4-0.4
=13.5-0.4
=13.1
5.6×1.25
=0.7×（8×1.25）
=0.7×10
=7
13.7×0.25-3.7÷4
=13.7×1/4-3.7×1/4
=（13.7-3.7）×1/4
=10×1/4
=2.5