Simple present:

I go to school. (Affirmative sentence)
I don’t go to school. (Negative sentence)
He plays cricket. (Affirmative sentence)
He does not play cricket. (Negative sentence)

Simple past:

She danced in cultural. (Affirmative sentence)
She did not danced in cultural. (Negative sentence)

Simple future:

I will write a letter. (Affirmative sentence)
I will not write a letter. (Negative sentence)