Answer:
This system has infinite solutions and it would be much easier to solve it by elimination but substitution it is.
Step-by-step explanation:
-3x+3y=9
-x+y=3
Isolate either x or y in any of the equations. I'll go with the second.
y = 3+x
Now substitute this for y in the first equation.
-3x+3(3+x)=9
Distribute the 3
-3x+9+3x=9
Combine like terms:
9=9
0=0
It's infinite
