The bond order in ${\mathrm{CO}}_3^{2-}\mathrm{ion}\mathrm{between}\mathrm{C}-\mathrm{O}\mathrm{is}$

We know that carbonate ion has following resonating structures

$\mathrm{Bond}\mathrm{order}=\frac{\mathrm{Total}\mathrm{number}\mathrm{of}\mathrm{bonds}\mathrm{between}\mathrm{atoms}}{\mathrm{Total}\mathrm{number}\mathrm{of}\mathrm{resonating}\mathrm{structure}}$

$=\frac{1+1+2}{3}=\frac{4}{3}=1.33$