Answer:
The best way to combine sentences 9 and 10 is the following: "At age nine, students began learning Latin, which was the language of international affairs."
Step-by-step explanation:
Sentences 9 a 10 were combined into a complex sentence. The independant sentence is "At age nine, students began learning Latin" and the subordinate clause is "which was the language of international affairs." In this case the pronoun"which" introduces the subordinate clause and makes reference to something that was mentioned before (Latin). The objective of the subordinate clause in this example to add information.