用递等式计算，能简算的要简算．
135÷27+12×4                   1620﹣1320÷60+80                （85+14×5）÷5
520÷[13×（43﹣33）]           490÷[210÷（360÷12）]           [160﹣（75+38）]×107
45+61+39+55                     25×5×4×2                        125×（8×5）×7．