a, 60%x + 2/3x =1/3.6 1/3
3/5x +2/3x =1/3.19/3
x.(3/5+2/3)=19/9
x.(9/15+10/15)=19/9
x.19/15=19/9
x=19/9:19/15
x=15/9
Vậy x=15/9
b,3.(3x-1/2)^3 +1/9=0
3.(3x-1/2)^3= -1/9
(3x-1/2)^3= -1/9:3
(3x-1/2)^3= -1/27
(3x-1/2)^3=(-1/3)^3
3x-1/2= -1/3
3x= -1/3-1/2
3x= -2/6+(-3/6)
3x= -5/6
x= -5/6 :3
x=-5/18
Vậy x=-5/18