Question

I can't pay you
(Rewrite making it affirmative)

Answer 1

I can pay you.

This would be the affirmative form of this sentence.

Answer 2

Answer:

I am unable to pay you.

Here the sentence is written in an affirmative tone maintaining the instruction that the negative word of the sentence has to be eliminated.

Can’t pay=unable to pay but here no negative word is used.

The meaning of the sentence is kept unchanged whereas the conversion from the negative to affirmative sentence is done perfectly.