The relationship between the sets of photos and the amount raised is an illustration of linear equations
<u>(a) Interpret the slope and the y-intercept</u>
From the graph, we have the following points
(x,y) = (0,25) and (1,40).
The slope (m) is calculated as:

So, we have:



The slope (15) means that, they charge $15 per photo they sold
The y-intercept is the point where x = 0.
So, the y-intercept is 25
This means that, they have raised $25 before they start selling the photos
<u>(b) Same slope but different y-intercept of 40</u>
This means that, they have raised $40 before they start selling the photos
<u>(c) Different slope of 12.5</u>
The slope (12.5) means that, they charge $12.5 per photo they sold
Read more about linear equations at:
brainly.com/question/13729904