This resource focuses on a subtraction warm-up exercise centered around a scenario involving a bison herd in Yellowstone. Students are presented with a situation where a herd of 842 bison has experienced a reduction in numbers as 567 of them move to a new valley. The main objective is to practice and become fluent in solving 3-digit subtraction problems that require regrouping. The material explains the process of regrouping, particularly when the top digit in a subtraction problem is smaller than the bottom digit, illustrating how to manage such situations effectively. Students are encouraged to show their regrouping steps in a designated area and are prompted to understand the significance of regrouping through a concept check question.