Learning goals: Teacher Facing Explain (orally and in writing) why adding or subtracting two equations that share a solution results in a new equation that also shares the same solution. Practice solving systems of linear equations by adding or subtracting equations to eliminate a variable. Use a context to make sense of an equation that is the sum of two equations in a system, and to reason about why this equation shares a solution with the system. Full lesson plan (warm-up, activities, synthesis, cool-down prompt) from Alg1.2 Linear Equations, Inequalities, and Systems, Algebra 1.