What are examples of a Simple a Compound a Complex and a compound-complex sentence?

Compound sentences have more than one independent clause. Complex sentences have dependent clauses. Compound-complex sentences have both.

(simple) My dog ate my homework.

(compound) My dog ate my homework, so I had to think up a good excuse.

(complex) My dog ate the homework that I left on the chair.

(compound-complex) My dog ate the homework that I left on the chair, but fortunately I still had the outline that I had written.