If NO3- has 3 resonance structures, but only one has to be written, where does the extra electron, making there then be 24 electrons, go if you cannot put brackets around the structure you are drawing?

Do you put -1 on both of the singly bonded Oxygens?...or where should the extra electron go???...it obviously does not go on the Nitrogen atom.

I figured out this problem. I ended up just putting the charges on each atom.