Answer:
[tex]a+9=9+a[/tex]
Step-by-step explanation:
Let [tex]a,b\in \mathbb R[/tex] then the commutative property of addition states that:
[tex]a+b=b+a[/tex]
This means that the order in which we add any two real numbers does not matter.
This implies that [tex]9+a[/tex] completes the given statement
[tex]a+9=9+a[/tex]
