This topic is in the 'Geometry' section. Even though you'll learn geometry in more detail in a geometry class, you'll be surprised by how much geometry you go over in PreAlgebra! The reason for this overlap is that in geometry you can draw shapes and lines and get a physical feel for the problems that you are working on. That makes solving abstract problems with variables a bit more intuitive, because you can rely on your visual intuition to make sense of the problem. The tutorials in this section are designed to make you comfortable with a lot of the basic vocabulary and concepts you'll come across as you work with different shapes, angles inside and outside of those shapes, parallel lines, and the idea of congruence. You'll see a lot of these concepts again in geometry class so if you learn them now, you'll be way ahead of the curve later!