standard_description: Prove that, given a system of two equations in two variables, replacing one equation by the sum of that equation and a multiple of the other produces a system with the same solutions.
problem_activity: Stage 3: Add 7, 8, or 9
Required Preparation
Materials to Gather
Number cards 0–10
Two-color counters
Materials to Copy
Blackline Masters
Five in a Row Addition and Subtraction Stage 3 Gameboard

Narrative
Students choose a number card 0-10 and choose to add 7, 8, or 9 to the number on their card and then place their counter on the sum.
Additional Information
Each group of 2 needs 25 counters.


aligns: no