Hello from MrBillDoesMath!
Answer: x = 2
Discussion:
As 3*ln(x) = ln (x^3) and 2 ln(4) = ln (4^2) the equation becomes
ln(x^3) + ln(4^2) = log(128) =>
ln (x^3 * 16) = log(128) =>
x^3 ^ 16 = 128 =>
x^3 = 128\16 = 8
If x cubed = 8, the the cube root is 2.
Thank you,
MrB