The Solution:
The given graph is of the form below:
We are asked if the people on the trail drink the same amount of coffee each day.
The given graph shows a negative relationship between pounds of coffee left and the number of days since leaving Fort Laramie, which means, the amount of coffee left decreases as the number of days increases. But the amount of coffee people drink each day is constant since the graph is a straight line and its slope is the same throughout the line.
Therefore, the answer is yes, people drink the same amount of coffee each day.