小红和小蓝练习跑步，若小红让小蓝先跑20米，则小红跑5秒钟就可追上小蓝；若小红让小蓝先跑4秒钟，则小红跑6秒钟就能追上小蓝．小红、小蓝二人的速度各是多少？
直接写得数==========
直接写得数=== 3÷8=========
直接写出得数． 93= 8.7﹣7=÷1= 21÷7= 7×÷7×= 44÷= 75÷10%= 0.9+99×0.9=
直接写出得数．
直接写出得数．÷=+=÷=×= 1÷0.25=÷1=÷3=﹣=
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= 3÷8=
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= 75÷10%= 0.9+99×0.9=
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