This document discusses ratios, proportions, and similar figures. It begins by defining a ratio as a comparison of two quantities using a fraction. It then provides examples of writing and interpreting ratios and unit ratios. The document explains that a proportion is when two ratios are set equal, and proportions can be solved using cross-multiplication. Examples are given for solving various types of proportion problems. The document concludes by defining congruent angles and similar figures, and providing examples of using proportions to solve for missing lengths in similar figures.