Answer :
To solve this question, we use the combination formula.
The combination formula is
[tex]^nC_r=\frac{n!}{r!(n-r)!}[/tex]Where n represents the amount of items in the set, and r represent the amount of items we want to select from this set.
For our problem, we have
[tex]n=9,r=7[/tex]Then, the combinations are given by
[tex]^9C_7=\frac{9!}{7!(9-7)!}[/tex]Solving this we have
[tex]\begin{gathered} ^9C_7=\frac{9!}{7!(9-7)!} \\ ^9C_7=\frac{9\cdot8\cdot7!}{7!(2)!} \\ ^9C_7=\frac{9\cdot8}{2!} \\ ^9C_7=\frac{9\cdot8}{2} \\ ^9C_7=9\cdot4 \\ ^9C_7=36 \end{gathered}[/tex]We have 36 combinations.