Answer:
D. x=29.37
Step-by-step explanation:
To answer this question you have to understand how log work. Log is the abbreviation of logarithm and it works as an inverse function of exponentiation.
The rules should be like this:
Variable a in the equation is called base. If it left empty you can assume its base 10. The log in this question using 5 as a base. Variable b will be x and variable c will be 2.1
Now, let's change the variable of the equation using the information from the question.