remember me mr woodward

why does 6x + 12 equal 3b if 2x + 4 is equal to b as opposed to b + 3 or b + 12 or 3b + 3 of 3b + 12. and also, who on this goddamn earth would have guessed that if x-2/3 = 1/36 then x must equal 216

song of the day flapper girl by the lumineers