Решение:
- В предложении "I'll be here next Monday," Charlie said., для преобразования прямой речи в косвенную, 'I'll be' изменяется на 'he would be', 'here' на 'there', 'next Monday' на 'the following Monday', и добавляется союз 'that'.
Ответ: Charlie said that he would be there the following Monday.