X is anonymous you do not know the value of X and less it says it on the problem and you cannot add 3X +2 because two is not a like term with three acts like term as if an equation was 3X plus 2X you can add that in that would equal 5X but since it’s 3X +2 you cannot solve that you can only simplify the equation but in your case it’s already simplified and you cannot do any work to that