Final answer:
1) graphs. 3) models. Economists use statistics, graphs, and models to understand how economic concepts function together.
Step-by-step explanation:
Economists use a variety of factual tools to understand how different economic concepts function together. These tools include statistics, which involve the collection and analysis of data to identify trends and patterns, as well as make informed decisions. Additionally, economists utilize graphs to visually represent data and show the relationship between different variables. Graphs can be particularly helpful in illustrating economic concepts such as supply and demand or comparing data between different entities.
Furthermore, models play a crucial role in economics. Models are simplified representations of real-world situations that help economists understand and analyze economic phenomena. For instance, economists may use mathematical equations to formulate and solve economic models that provide insights into various economic issues or problems.