Đáp án:
`a)`
` (2/5 -x)^3 = (-8/27) = (-2/3)^3`
` => 2/5 - x = -2/3`
` => x= 2/5 +2/3`
` => x= 16/15`
`b)`
` 4/3 : x = 3/4 : 2/5`
` 4/3 : x =15/8`
` x =4/3 : 15/8`
` x =32/45`
`c)`
` 1/(2) *x : 8/7 = 0,03 * 4/11`
`=> 1/(2) *x : 8/7 = 3/275`
` 1/(2) x = 24/1925`
` x = 48/1925`