How to pronounce three

Since we rarely exercise the front of our tongue, we have very weak tongue muscles in that area, which explains why we often have difficulty pronouncing L or R, consonants that requires the use of the front muscles of our tongue a lot.

People who say “free” instead of “three” either were not taught growing up, or are incapable, of placing their tongue behind the upper teeth in the way necessary to produce the “th”. Instead they take the lazy way and don’t use their tongue at all.