Xx is a somewhat special letter in written English because it does not represent its own unique phoneme. In fact, it often serves to represent more than one phoneme in a word. For this reason, instructors may devote time in an introductory cued English class to covering how words with Xx are cued.
The most common pronunciation for the letter x is a combinations of /kkk/ and /sss/ as in Texas, mix, flax, six. Another common pronunciation is the combination of /ggg/ and /zzz/ as in example and exist. Some words may may be pronounced with either combination. For example, exit may be pronounced with /ks/ or /gz/. Which combination is used may be a function of one’s dialect or the part of speech. For some cuers, one combination may be used for the noun and the other for a verb:
Notice that the addition of either /sss/ or /zzz/ to the preceding consonant follows the same voicing rule that occurs with addition of plural -s. Voiceless /kkk/ takes voiceless /sss/. The voiced consonant /ggg/ takes the voiced consonant /zzz/. So, while a word may be pronounced with either /ks/ or /gz/, it is unlikely to mix those combinations. In other words, */kz/ or */gs/ are unlikely pronunciations for native English users.
The letter Xx has several other possible pronunciations. At the beginning or words, it may be pronounced as /zzz/. The following table provides a few of the less common pronunciations of this tricky letter.