If you mean this:
$$2 log(2^{3x}) = 4$$
Then it's not too difficult to solve. First, move the 2 over.
$$log(2^{3x}) = 2$$
Then, by the logarithmic power rule,
$$log(2^{3x}) = 3x \times log(2)$$
$$3x = \frac{2}{log(2)}$$
$$x = \frac{2}{3 log(2)}$$
If you mean this:
$$2 log(2^{3x}) = 4$$
Then it's not too difficult to solve. First, move the 2 over.
$$log(2^{3x}) = 2$$
Then, by the logarithmic power rule,
$$log(2^{3x}) = 3x \times log(2)$$
$$3x = \frac{2}{log(2)}$$
$$x = \frac{2}{3 log(2)}$$
