I assume we are solving for x?
You need to isolate x on one side of the equation.
subtract 4x from both sides. This leaves -2x+3=-3. Because we need to isolate x we subtract 3 from both sides, leaving -2x=-6. Again we isolate x, divide both sides by -2. x=3
2x+3=4x-3
-2x+3= -3
-2x= -6
x=3