The number of words (with or without meaning) that can be formed...

Consonants are $L, T, T, R$

Vowels are $E, E,$

Total number of words (without meaning) from letters of word $' LETTER ' = \dfrac{6 !}{2 ! 2 !} = 180$

Total number of words (with or without meaning) from letters of word $' LETTER '$ if vowels are together $= \dfrac{5 !}{2 !} = 60$

$∴$ Required $= 180 - 60 = 120$