To solve for y, we need to isolate y on one side of the equation. We can do this by subtracting 3x from both sides of the equation:
3x + y - 3x = 3 - 3x
Simplifying the left side gives:
y = 3 - 3x
So the solution for y is:
y = -3x + 3
Therefore, y is equal to negative 3 times x plus 3.