递等式计算．（能简算的要简算）
9.6÷0.4×0.25                 29.7÷（5.85÷0.65）
7.4×9.9                       3.84﹣2.7×0.64
8.68﹣8.68÷0.56×0.5          4.7×4.7+4.7+4.3×4.7．