My initial guess is that 'x2' was intended to be 'x^2' (x-squared).  Otherwise there is no real means of 'checking the answer' for the equation 'x2=3x-2' other than replacing one of the 'x' values with the final numeric result.  The images below highlight each of these statements. 

So if 'x^2' was not intended, then the initial equation could be "checked" as follows: