Tracy has a collection of sea shells from several trips to the beach. Before her last trip, she had 317 shells. On Wednesday, she picked up 129 shells. On Friday she decided not to keep 84 of the shells she picked up on Wednesday. Using the number line below, show how she can figure out how many shells she has in her entire collection after Friday’s decision. Then write two equations that match the model of the number line.
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3.5 Algebraic reasoning. The student applies mathematical process standards to analyze and create patterns and relationships. The student is expected to: