Final answer:
The proper noun in the sentence 'he gave her tickets to a show in Baltimore.' is 'Baltimore', which should be capitalized as it's the name of a city.
Step-by-step explanation:
In English grammar, a proper noun is the name of specific entities, like people, businesses or cities, and they are always capitalized. In the sentence you've given, 'he gave her tickets to a show in Baltimore.', the proper noun is 'Baltimore'. 'Baltimore' is a city, and therefore a proper noun, and it should always be capitalized.
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