Answer:
A complex sentence is a sentence using at least one dependenet clause. A compound-complex sentence has at leas two independent clauses and at least one dependent clause.
Step-by-step explanation:
A complex sentence example: Because I didn't know the answer, I searched it up. The dependent clause is "Because I didn't know the answer" because it can't be a sentence by itself.
A compound-complex sentence example: Because I didn['t know the answer, I searched it up, but I still didn't understand it. The independent clauses are "I searched it up" and "I still didn't understand it". "But" is a preposition and isn't part of the clause.