Since \( FK \) is the perpendicular bisector of \( GJ \), the distances from point \( F \) to points \( G \) and \( J \) must be equal. Therefore, we can set up the equation based on the lengths given:
\[ GF = JF \]
Substituting the provided lengths into the equation, we get:
\[ 6 + x = 3x - 5 \]
Now, we will solve for \( x \):
- Start by rearranging the equation to move all terms involving \( x \) to one side:
\[ 6 + x + 5 = 3x \]
This simplifies to:
\[ 11 + x = 3x \]
- Now, isolate \( x \) by subtracting \( x \) from both sides:
\[ 11 = 3x - x \]
This simplifies further to:
\[ 11 = 2x \]
- Divide both sides by 2 to solve for \( x \):
\[ x = \frac{11}{2} = 5.5 \]
Thus, the value of \( x \) is:
\[ \boxed{5.5} \]