脱式计算，能简算得要简算．
5.45+0.56×7.4            2.5×0.89×4              25×16.7﹣25×0.7
7.6×99                   5.6×10.2                 2.5×3.2×1.25
9.6÷0.4×0.25            3.56×2.8﹣1.24×0.9     （12.5+1.25）×8
（2.5×1.7）×4           12.5×8.8                 0.89×100.1
0.25×0.8×4×0.125       8.4×0.26+0.74            31.7﹣0.5×0.7﹣1.65．