We use a question tag when we want to check that something is true or to ask for agreement .

The soup is very good,isn't it? Yes ,it is.

After an affirmative sentence ,we use an affirmative question tag.

a) If the main sentence has an auxiliary verb or the verb to be ,we use this in the question tag.

She 's pretty, isn't she ?

He isn't very clever,is he ?

b)If the main sentence has no auxiliary verb,we use do/does or did in the question tag.

She likes animals,doesn't she ?

He came with you,didn't he ?

c) When the subject of the main sentence is a noun, we use a pronoun in the question tag.

Sally speaks French,doesn't she?