`e)`
`0,01 : 2,5 = (0,75x) : 0,75`
`=> 1/250 = (3/4x) : 3/4`
`=> 3/4x = 1/250 . 3/4`
`=> 3/4x = 3/1000`
`=> x = 3/1000 : 3/4`
`=> x = 1/250`
Vậy `x = 1/250`
`f)`
`1 1/3 : 0,8 = 2/3 : (0,1x)`
`=> 4/3 : 4/5 = 2/3 : (1/10x)`
`=> 2/3 : (1/10x) = 5/3`
`=> 1/10x = 2/3 : 5/3`
`=> 1/10x = 2/5`
`=> x = 2/5 : 1/10`
`=> x = 4`
Vậy `x = 4`