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 steam locomotive to be built in America was the Tom Thumb by Peter Cooper. The Tom Thumb had its first run in 1830, hauled 36 passengers and went 18mph. In 1830, the steam locomotive known as The Best Friend of Charleston was the first locomotive to pull cars in America and regularly carry passengers.