If Jeff is either overtly expressive and likes to talk to strangers or neither overtly expressive nor likes to talk to strangers, then Jeff is neither an extrovert nor likes to talk to strangers.
All extroverts are overtly expressive. People are either extroverts or introverts. If someone is an introvert, then they are shy and reticent.  No shy and reticent person likes to talk to strangers. Jeff is not an extrovert and someone who likes to talk to strangers.
∀x (Extroverts(x) → OvertlyExpressive(x))  ∀x (Extroverts(x) ∨ Introverts(x))   ∀x (Introverts(x) → ShyAndReticentPerson(x))  ∀x (ShyAndReticentPerson(x) → ¬LikeToTalkToStrangers(x))  ¬Extroverts(jeff) ∧ ¬LikeToTalkToStrangers(jeff)