Yes, the two equations are equivalent.
For the first equation, we can combine like terms. The equation becomes 3x = 9. From there, we can divide both sides by 3 to get the value of x. After dividing, we see that
x = 3. Now onto the second equation, we can add 4 onto both sides to isolate the variable, and the equation becomes 3x = 9, which is the same as the first equation. We can do the same division and see that x = 3. Both variables are the same value in both equations, so yes, the equations are equivalent.
