Answer:
The equations 3x + 12 = 6 and -2 = 4 -3x are not equivalent .
Explanation:
3x + 12 = 6....i) 
Firstly taking equation ...i) and solving for x  
=> 3x = 6-12 
=> 3x = -6 
=> x = -6/3 
=> x = -2 
Then equation ...ii) 
-2 = 4 -3x.....ii) 
=> 3x = 4+2 
=> 3x = 6 
=> x = 6/3 
=> x = 2 
Hence , 2 ≠ -2 
and the equations are not equivalent ..