Depending on the equation there can be three possible cases:
 
 1- There can be 1 specific solution for the variable:
 
  2x+4= 3 
 
  where x= -1/2
 
 
 
 2- there can be an infinite amount of solutions: 
 
  2x+x-2=3x-3+1
 
  where x=x 
 
 
 
 3- there can be no answer: 
 
  3+2x-x=5-3x+4x
 
  where the solution doesn't exist