Đáp án:
`1 1/3 : 0,8 = 2/3 : (0,1x)`
`<=> 4/3 : 4/5 = 2/3 : (1/10 x)`
`<=> 5/3 = 2/3 : (1/10 x)`
`<=> 2/3 : (1/10 x) = 5/3`
`<=> 2/3 : x/10 = 5/3`
`<=> 2/3 . 10/x= 5/3`
`<=> 20/(3x) = 5/3`
`<=> 20.3= 3x.5`
`<=>3x.5=20.3`
`<=> 15x = 60`
`<=> x= 4`
Vậy `x=4`