Threteen or Thretteen: How To spell?
The word Threteen is misspelled against Thretteen, an adjective meaning "Thirteen."
Thretteen has double "tt" is mispronounced as "t"Remember double 'TT' in between the strings thre & een which should not be misspelled with single 'T'
Wrong Spelling:  thre-t-een  Correct Spelling:  thre-tt-een 
Explore spell check of Thretteen to spell without errors.