Answer:
1. Linear; 2. C = 2.50x + 40  
Step-by-step explanation:
1. Prediction
Yes, it is a linear function, because each additional photo adds the same amount to the cost.
2. Equation
          Let C = the cost of the photo package
          and x = the number of photos
Then 2.50x = the cost of the photos
     And $40 = cost of photo shoot
       Then C = 2.50x + 40
The figure below shows that the graph of your equation is a straight line.