Answer and Explanation:
Let's answer each question separately:
Which subordinating conjunction correctly completes this sentence? Mandy practiced karate every day, _____ she failed to beat her final opponent.
yet
in order to
if
The correct subordinating conjunction to be used is "yet". This conjunction indicates contrast between the ideas expressed in the different sentences. In this case, the first idea is that Mandy practiced really hard. The second idea is that she lost. "Yet", just like "but" or "nevertheless", shows how those two ideas sort of oppose each other, since we expect someone who practices diligently to win. Therefore:
Mandy practiced karate every day, yet she failed to beat her final opponent.
Which sentence uses a coordinating conjunction? Even though you want to relax, we should go to the party. We could stay in tonight. We could go to the party tonight, or we could stay in. We could go to the party tonight.
Coordinating conjunctions are used to join two independent clauses. They are: for, and, nor, but, or, yet, so. With that in mind, it is easy to see that the sentence that uses a coordinating conjunction is: We could go to the party tonight, or we could stay in. The conjunction "or" indicates an alternative.