Although many factors affect students' mathematical activity during a lesson, the teacher's selection and implementation of tasks is arguably the most influential in determining the level of student engagement. Mathematical tasks are intended to focus students' attention on a particular mathematical concept and it is the careful developing and sequencing tasks that encourage students' independent exploration of mathematical ideas. To assist mathematics teachers in their selection and implementation of tasks, they need to first answer the questions: (1) what tasks promote contextual reasoning? (2) What is contextual reasoning? (3) Why is it important? And (4) how do we (teachers) get students to engage in contextual reasoning? This article presents a highly-cognitive-demand analysis to help students build a deep and robust understanding of the underlying mathematical concepts by examining the steps: (1) Context and Reasoning, (2) Reasoning and Assumptions, (3) Assumptions and Responses, (4) Responses and Focus, And Finally (5) Focus and Engagement. When teachers incorporate opportunities to reason about the mathematical context in everyday tasks they promote student engagement in verifying and validating mathematical rules or ideas.