Resposting this–

This is a semi educated guess, I am not knowledgable about electricity.

Let  E= k/d       and    C=md    whee  k and m are constants. (but we do not need to worry about C.)

and d is the distance between the chages. 

Initially  

$\frac{k}{d}+\frac{k}{d}+\frac{k}{d}=\frac{3k}{d} = 15J$

Now move the charge and the distances become    d/2, d/2  and d

so new energy is

$\frac{k}{d/2}+\frac{k}{d/2}+\frac{k}{d}=\frac{5k}{d} = 15*5/3\;Joules = 25J$

So if my reasoning is correct there will be 10 more Joules of energy.

Thank you so much Melody!

Yes, it is! Your solution is really helpful!