Lesson 2: Substitution & Elimination in Real World Scenarios
Duration of Days: 3
Lesson Objective
Solve systems of linear equations algebraically using both substitution and elimination methods, and apply these strategies to model and solve real-world scenarios featuring two distinct constraints.
When looking at a system of equations, what structural features make it easier to solve using substitution rather than elimination (and vice versa)?
Why is an algebraic solution more reliable than a visual solution found by graphing?
How do we translate separate real-world conditions or pricing rules into a cohesive system of two algebraic equations?
What does it mean if the variables cancel out entirely while solving algebraically, leaving a statement like 0=0 or 0=5?
Algebraic method, Substitution method, Elimination method, Coefficient, Constant, Contextual constraint, Solution verification, Inconsistent system (No solution), Dependent system (Infinitely many solutions)
CCSS.MATH.CONTENT.8.EE.C.8.B, CCSS.MATH.CONTENT.8.EE.C.8.C
Students transition from visual estimation to precise algebraic calculation.
DOK Level: 3 (Strategic Thinking / Contextual Modeling)
When multiplying an entire equation by a constant to set up elimination, students frequently forget to multiply the constant term on the right side of the equal sign.
Forgetting to apply the distributive property to a negative sign when substituting an expression into a set of parentheses.
Provide a reference sheet highlighting when to use substitution
Exit Ticket
Tasks