Montana Math MT.8.EE.8

Math8th GradeExpressions and Equations

The Standard

Analyze and solve pairs of simultaneous linear equations by: Understanding that solutions to a system of two linear equations in two variables correspond to points of intersection of their graphs, because points of intersection satisfy both equations simultaneously, Solving systems of two linear equations in two variables algebraically, estimating solutions by graphing the equations, and solving simple cases by inspection, and Solving problems in context that lead to two linear equations in two variables. This standard should incorporate cultural context relating to Montana Indigenous Peoples and local communities.

2026 Montana Mathematics Content Standards

Teacher's field guide

What This Standard Means

What Students Need to Do

Students graph two lines and estimate where they cross. They find the exact point with algebra and check it in both equations. They write two equations for a local situation and explain what the shared point means.

What Mastery Looks Like

A student can estimate an intersection from a graph, solve for its coordinates, and check both equations. They recognize that parallel lines have no solution and identical lines have infinitely many solutions.

Common Misconceptions

Students may think a point on one line solves both equations. They may treat a graph's rough estimate as exact or swap the meanings of the two variables. Some give (0,0) as the solution for parallel lines.

How to Assess It

Exit ticket: Graph y=2x+1 and y=-x+7, estimate their crossing, then solve algebraically and check the point in both equations.

Lesson moves

Ways to Teach It

  1. Graph y=2x+1 and y=-x+7 on separate transparent grids, stack them, and mark the shared point.

  2. Have partners explain why (2,5) satisfies both equations but (1,3) satisfies only y=2x+1.

  3. Give pairs equation cards to solve by substitution, including one pair with parallel lines and one with identical lines.

  4. Model two proposed ride plans for students traveling to a Montana Tribal college: C=12+4r and C=4+6r; find the break-even ride count.

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