Final answer:
Economic variable data comes in time series and cross-sectional forms, both of which are crucial for analyzing and solving economic models either algebraically or graphically.
Step-by-step explanation:
When looking at a single economic variable, data can come in two main forms: time series data and cross-sectional data. Time series data tracks changes in a variable over time, providing a chronological sequence of data points that can be used to identify trends, cycles, or seasonal patterns. Cross-sectional data, on the other hand, analyzes a variable at a specific point in time across different entities, such as countries or individuals, allowing for comparisons and distributions to be observed. Both forms of data are crucial for analyzing, interpreting, and solving economic models either algebraically or graphically, with graphs serving as a tool for illustrating data visually through line graphs, pie charts, and bar graphs.