Final answer:
The Inca used Quipu, a system of knotted strings, for record-keeping since they lacked a formal writing system. Quipus were a critical tool in administering the Incan empire, containing both quantitative and qualitative data.
Step-by-step explanation:
The Inca lacked a formal writing system and instead utilized Quipu, a sophisticated system of knotted strings for record-keeping and communication. The Quipu system consisted of various colors, lengths, and types of knots tied to strings, which conveyed different types of information. These intricate devices were essential in maintaining the socio-economic structure of the Incan empire, used by the Quipucamayoc (knot keepers or record keepers) to track data such as census, taxes, resources, and even historical events. Although the precise knowledge about their complete usage and significance has been lost, particularly due to the destruction wrought by the Spanish conquest, modern scholars continue to study the surviving Quipus to reveal insights into the Incan civilization.