Answer:
1. Tents kept the rides in great condition during extreme weather. - Simple
2. The fair setup began late in July, and it ended at the beginning of September. - Compound
3. When fair-goers bought tickets, they often purchased too many. - Complex
4. Although some people got sick from riding, the extreme roller coaster was popular, and there was always a very long line. - Compound-complex
Explanation:
1. A simple sentence is constituted of a single independent clause. It has a subject and a predicate, and it expresses a complete thought.
2. A compound sentence is formed by joining two independent clauses. We connect them by using a coordinating conjunction - for, and, nor, but, or, yet, so.
3. A complex sentence is formed by joining an independent clause and a dependent one. A dependent clause needs the independent one to give it context, so that it makes sense. Subordinating conjunctions should be used, such as when, where, if, though, etc.
4. A compound-complex sentence is formed by two independent clauses and a dependent one, at least.
