f.4 math help~~

(1)
3x^(-1/3)-1=8
Let y=x^(-1/3)
3y-1=8
3y=9
y=3
x^(-1/3)=3
1/x^(1/3)=3
x^(1/3)=1/3
x=1/3^(1/3)

(2)
2(1/3x-1)^(-3)=54
If you mean:
Situation 1:
2[1/(3x-1)]^(-3)=54
[1/(3x-1)]^(-3)=27
1/(3x-1)=27^(-1/3)
3x-1=3
3x=4
x=4/3
Situation 2:
2(1/3x -1)^(-3)=54
(1/3x -1)^(-3)=27
1/3x -1=1/3
1/3x=4/3
3x=3/4
x=1/4

Q.1 3x^(-1/3)-1=8
3x^(-1/3)-1=8
3x^(-1/3) = 9
x^(-1/3) = 3
(x^-1/3)^3 = 3^3
x^-1 = 27
x = 1/27

Q.2 2(1/3x - 1)^-3=54
2(1/3x - 1)^-3=54
(1/3x - 1)^-3=27
(1/3x - 1)^3=1/3^3
1/3 x – 1 = 1/3 (全式乘 3)
x – 3 = 1
x = 4