This document discusses methods for solving systems of linear equations with two variables: graph method, substitution method, elimination method, and substitution-elimination method. It also presents a word problem about determining the current ages of a father and son given the difference in their ages is 26 years and the sum of their ages was 34 years five years ago, asking the reader to consider what information is provided, how to model the problem mathematically, what mathematics topic is relevant, and how they would solve it.