The table BELOW shows the marks scored by a group of students in a class test. If the mean score is \(3.4\), find \(x\).
\begin{array}{|l|l|l|l|l|l|}
\hline Score & 1 & 2 & 3 & 5 & 6 \\
\hline Frequency & 3 & 6 & 7 & \(x\) & 4 \\
\hline
\end{array}