a) Using your equation from step 2d, estimate the GPA of a student who studies for 15 hours a
week. Justify your answer.

Answer:
The predicted GPA is then y = 0.149(15) + 0.89 = 3.1
Step-by-step explanation:
Although you don't specifically say so, the equation you provide here is probably a "best fit" equation based upon data: GPA versus the number of hours of study per week.
y = 0.149x + 0.89 and the number of study hours of interest is 15.