Đáp án:
$a/$ `4/5x = (-2)^3/(|-7| . 5)`
`-> 4/5x = (-8)/(7 .5)`
`-> 4/5x = (-8)/35`
`-> x = (-8)/35 : 4/5`
`-> x =(-2)/7`
`text{Vậy}` `x = (-2)/7`
$b/$ `(-1)/2x + 2/3. (-5)/4 = 3/5x - 5/6`
`-> (-1)/2x - 5/6 = 3/5x - 5/6`
`-> (-1)/2x - 5/6 - 3/5x + 5/6 = 0`
`-> [(-1)/2x - 3/5x] + (-5/6 + 5/6) = 0`
`-> [(-1/2 - 3/5)x] + 0 = 0`
`-> (-11)/10x = 0`
`-> x = 0`
`text{Vậy x=0}`