This answer is not correct. I think that you thought that there was a single bond to one of the oxygen atoms and a double bond to the other oxygen atom. That is the case with NO₂^- but not with this ion. Try redrawing the electron-dot formula and make sure that you count your electrons carefully so that you have the correct number of electrons for the formula. You also added the total number of bonds to get the bond order. The bond order is the average of all the bonds.