grammar: Usage of relative pronoun

[Hothu]

Please explain how to reduce relative clauses to To-infinitive phrases.
I have 2 following sentences, combine them with a relative pronoun; then reduce it to a phrase:
"He doesn't let anything disturb him. He isn't that type of person."
Please help me.

[Mister Micawber]

.
He doesn't let anything disturb him. He isn't that type of person.

He isn't the type of person who lets anything disturb him.

He's not the type of person to let anything disturb him.
.
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Native English teacher at Mister Micawber's