3∶9=∶15 =
∶3=4∶ 0.5∶=∶12
(x-0.5)÷3=
56705769 999910000
31942989 70867068
9800 8009 9008 9900 10000
<<<<
428<4239 300<3800
550<5600 224<2254
9.9×5.9 60 1