ANSWER
The solution is [tex](-1,9)[/tex]
EXPLANATION
We want to solve the simultaneous equations
[tex]y=-3x+6---(1)[/tex]
and
[tex]y=9--(2)[/tex].
We substitute equation (2) in to equation (1), to obtain
[tex]9=-3x+6[/tex]
This has now become a linear equation in a single variable [tex]x[/tex].
We solve for x by grouping like terms.
[tex]9-6=-3x[/tex]
[tex]3=-3x[/tex]
We divide through by negative 3 to get;
[tex]-1=x[/tex].
Hence, the solution is [tex](-1,9)[/tex]
