Meth/Math, whats the difference?

Brian had a rap station on the TV a few weeks ago.  The song that came on was about drinking wine/smoking pot (or whatever the cool term for this is these days).  I was half joking, half seriously talking to the boys and said something like, "Please be careful when you drink alcohol and don't do drugs and DEFINITELY don't do meth! (Brian and I have been watching Breaking Bad and meth is sadly on my mind too often)."  Landon's face got pretty serious and a little sad and before long he looked at me with his sweet innocent eyes and said, "but mommy, I really love math!"