Answer:
![\log_2 16 = 4 ~~\Longleftrightarrow ~~ 2^4 = 16](https://img.qammunity.org/2020/formulas/mathematics/high-school/dkdyxb8iugoc7dwjku5vq4c6f9bj6al6iv.png)
Explanation:
![\log_b x = y ~~\Longleftrightarrow ~~ b^y = x](https://img.qammunity.org/2020/formulas/mathematics/high-school/nc7exqtnr8e03o5yp330tjal1q8zxxrtc2.png)
![\log_2 16 = 4 ~~\Longleftrightarrow ~~ 2^4 = 16](https://img.qammunity.org/2020/formulas/mathematics/high-school/dkdyxb8iugoc7dwjku5vq4c6f9bj6al6iv.png)
Keep in mind that a log is an exponent.
When you are asked for the log base 2 of 16, you are being asked for the exponent you need to raise 2 to, to get 16. The base in the log is the same base as in the exponential form.
In other words, the question "what is log base 2 of 16?" is the same as the question "what exponent do you raise the base 2 to to get 16?"