Answer and Explanation:
There are two sentences in this question. Let's analyze them separately.
<em>When the clock chimed three, the school bell rang, and the children raced to the bus.</em>
Independent clauses: <em>the school bell rang, and the children raced to the bus. </em>("and" is a coordinating conjunction)
Subordinate clause: <em>When the clock chimed three </em>("when" is a subordinating conjunction)
Therefore, what we have here is a <u>compound-complex sentence</u> - formed by <u>two independent clauses and a dependent/subordinate one</u>, at least.
<em>The Northwest is damp and rainy, but the Southwest is dry.</em>
Independent clauses: <em>The Northwest is damp and rainy, but the Southwest is dry. </em>("but" is a coordinating conjunction)
Subordinate clauses: none
Here, we have a <u>compound sentence</u> - formed by joining<u> two independent clauses</u> connected by a coordinating conjunction - for, and, nor, but, or, yet, so.