Substituting (x, y) with (a, a), since we have:
3a=2a-4, which means that 3a-2a=-4, that is a=-4.
So, the point is (-4, -4).
Remark: a point which lies in the graph of an equation is a solution of that equation. So x=a, y=a satisfies the equation 3y = 2x -4, which makes our substitution legitimate.
Answer: (-4, -4).