We have such system
[tex] \left \{ {{y=4x-9} \atop {y=x-3}} \right. [/tex]
We can take first equation and put value of y in terms of x into second eq, so
y=x-3
4x-9=x-3 now we can solve it
4x-9=x-3 /-x both sides
3x-9=-3 /+9 both sides
3x=6 /:3 divide by 2 both sides
x=2 --- its the result