The total number of dative bonds present in all the following $\mathrm{CO}, {\mathrm{NH}}_4\mathrm{Cl}, {\mathrm{Al}}_2{\mathrm{Cl}}_6, \mathrm{Al}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6, {\mathrm{HNO}}_3$ and ${\mathrm{CO}}_2$ is

So according to the question we have to find the dative bond present in the following such as 

So we know that in

1. Carbonyl compound it contains one dative bond
2.  Ammonium ion also contains one dative bond 
3.  ${\mathrm{Al}}_2{\mathrm{Cl}}_6$ contains the bridge bond that's why it contains two dative bonds
4.  $\mathrm{Al}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6$ contains the bridge bond that's why it contains two dative bond 
5. ${\mathrm{HNO}}_3$ contains one dative bonds

So  total $7$ dative bonds are present in the following compound