Hello Renebed,

I hope your Calculus studies are going well.  You didn't leave written instructions on how you want to solve this, but I am assuming that you want to solve the function when x is equal to 3. You can do this by plugging 3 into the equation:

F(3) = ln 3

You can check out the following articles to learn more about solving F(x) = ln x  functions.

Derivatives of Exponential and Logarithmic Functions for AP Calculus
http://www.education.com/reference/article/derivatives-exponential-logarithmic-functions/

Evaluating Basic Integrals for AP Calculus
http://www.education.com/reference/article/antiderivatives-integration-formulas/

Happy studying,

Hayley

Additionally, this article can give you insight about solving equations when x is specified. Scroll to the bottom of the article to see Example 5, which shows a natural logarithm.

Graphs of Derivatives for AP Calculus
http://www.education.com/reference/article/graphs-derivatives/