Answer: The equation for the 7th grade is y = 5x + 7, where y is the total number of items collected and x is the number of days. The initial value is 7 and the slope is 5.
The equation for the 8th grade is y = 8x + 20, where y is the total number of items collected and x is the number of days. The initial value is 20 and the slope is 8.
Therefore, the 8th grade has a greater slope (8) compared to the 7th grade (5). The 8th grade also has a greater initial value (20) compared to the 7th grade (7).
Explanation: