How should the subject-verb agreement in this sentence be changed, if at all? Both the ranger and the camper sees the bear.

The sentence should be changed as there is no subject-verb agreement. The correct form of the verb should be in plural instead of singular. So the correct sentence is "Both the ranger and the camper see the bear."

Even though both subject nouns are singular (ranger and camper), the rule of compound subject applies here. In this case singular nouns are united by the preposition "and" to make a plural subject. Therefore, the verb should be in the plural (see) to have subject-verb agreement.

Both the ranger and the camper see the bear.

Explanation:

The subject is plural so the verb is see. If the subject were singular as in " the ranger", it would be "sees the bear".