It's and easy question if you know what to do.
Think about it this way, when you square a number, what is the reverse operation? A square root.
Hence, \(\displaystyle \begin{array}{l}
8^2 = 64 \\
\sqrt {64} = 8 \\
\end{array}\)
In this case, you want to solve for x. So consider this, what is the reverse operation for trig functions? Their inverse functions.
\(\displaystyle \begin{array}{l}
\tan (x) = \frac{7}{{11}} \\
x = \tan ^{ - 1} \frac{7}{{11}} \\
\end{array}\)
It's almost purely a calculator problem, unless you are dealing with special angles.