Yes, that is exactly what you should tell them. 1  If two clauses are connected with a coordinating conjunction, it's a compound sentence. 2  If two clauses are connected with a subordinating conjunction, it's a complex sentence.
Trains were first- 1784, but cars weren't invented until 1890.
The first car I bought was for my father, says P.K. Subban. I didn't want to see myself driving around in a nicer car than him. The first car I bought was for my father, says P.K. Subban.