For the first question about which social class had the most people in Ancient Egypt, the answer would be Farmers and Slaves. They comprised the largest portion of the population due to the agrarian nature of ancient Egyptian society.
For the second question regarding which social classes were most likely to read and write, the answer would be Scribes. Scribes were trained to read and write and held significant roles in administration, record-keeping, and communication. Other classes, such as Pharaohs and Government Officials, Nobles, and Priests, may have also had some literacy, but Scribes were the primary literate class.