approximation of $\frac{6\ln 10}{\ln 2}$?

Using the change of base formula, we find that $\frac{ln10}{ln2} = log_2(10)$, which is between 3 and 4... so $5n$ is 30 times this.

Since $6 \ln 10 = \ln(10^6)$, the question asks: $10^6$ is approximately what power of 2?

You probably know that in science, "kilo" means 1000, but on computers a kilobyte is 1024. Why the strange number? Because it is a power of 2, and computers like powers of 2. So remember this: $10^3 \approx 2^{10}$. For your problem, square to get $10^6 \approx 2^{20}$. So your answer is approximately $20$.