Answer:
Infinitely many solutions.
Step-by-step explanation:
Given
[tex]y = -x + 3[/tex]
[tex]3x + 3y = 9[/tex]
Required
Using substitution method, solve
Substitute -x + 3 for y in [tex]3x + 3y = 9[/tex]
[tex]3x + 3(-x + 3) = 9[/tex]
Open bracket
[tex]3x - 3x +9 = 9[/tex]
[tex]9 = 9[/tex]
[tex]0 = 0[/tex]
The above shows that there are infinitely many solutions.