脱式计算，能简算的要简算

①7.25÷1.25÷8

②1.8×25＋24÷1.5

③99×0.24＋9.9×7.6

④0.175÷0.25×0.4

⑤3.74+0.625÷25

⑥0.68÷（5.2 -3.5）×1.25