Преобразуйте прямую речь в косвенную.
Nick: What are you doing, Mary?
Mary: I am writing a letter to Lucy.
Nick: Writing a letter?! You cannot read.
Mary: Never mind. Lucy cannot read.

Nick said what Mary was doing that moment.Mary answered that she was writing a letter to Lucy. Nick asked to repeat if she was writing a letter. he added that Mary could not read. Mary answered that Lucy couldn't read.