Answer:
-78
Step-by-step explanation:
[tex]8m - n + 3 \\ if \: n \: = \: 9 \: m = \: - 9[/tex]
[tex]8( - 9) - 9 + 3 [/tex]
[tex] = - 72 - 9 + 3[/tex]
[tex] = - 81 + 3[/tex]
[tex] = - 78[/tex]
