To solve the equation \( x^3 = 64 \), we need to find the value of \( x \).
Taking the cube root of both sides, we have:
\[ x = \sqrt[3]{64} \]
Since \( 64 = 4^3 \), we have:
\[ x = 4 \]
Now, let's check the options:
- \( x = 4 \) (this is correct)
- \( x = 8 \)
- \( x = 6 \)
- \( x = 21 \)
The only correct answer is:
\( x = 4 \).