b) You have the following expression:
[tex]x^3=\frac{27}{64}[/tex]Take into account that 27/64 can be written as follow:
[tex]\frac{27}{64}=\frac{3}{4}\cdot\frac{3}{4}\cdot\frac{3}{4}[/tex]Then, x = 3/4
c) For the following expression:
[tex]x^3=\frac{1}{8}[/tex]you can write it as follow:
[tex]\frac{1}{8}=\frac{1}{2}\cdot\frac{1}{2}\cdot\frac{1}{2}[/tex]Then, x = 1/2