Lời giải :
`a) x/10-(x/30+(2x)/45)=4/5`
`⇔x/10-x/30-(2x)/45=4/5`
`⇔(9x)/90-(3x)/90-(4x)/90=72/90`
`⇔9x-3x-4x=72`
`⇔2x=72`
`⇔x=36`
`b) 5(2x-1)/18+x+3/12=7x+3/6-2(3-x)/9`
`⇔10(2x−1)+3(x+3)=6(7x+3)−8(3−x)`
`⇔20x−10+3x+9=42x+18−24+8x`
`⇔23x−1=50x−6`
`⇔27x=5`
`⇔x=5/27`