This solving systems of linear equations by substitution lesson is very comprehensive. It is meant to be taught over 2 or more days, but can be reduced to 1.5 days for honors classes, etc.
Please check out the preview document to understand the way the example problems are explained and to better understand the quality of the lesson.
The lesson includes: 2 warm-ups, the basics of substitution and an understanding of equality/balance/weight, numerous examples of all types of substitution problems, and 4 word problems.
Additionally, the guided notes pages I created to accompany this lesson are also available at: