Look closely at the graph. As you may be able to see, the line starts at halfway point just between 60 and 40. With common math sense, you may be able to determine that the starting point is $50.
Now, time for answer elimination.
A. is wrong, even-though the graph DOES show that she saves $10 each week, this question is asking for the >>>>INITIAL VALUE<<<<
B. Is wrong, because once again, even-though it's true that she had 90 dollars on week 4, the question's asking for the >>>>INITIAL VALUE<<<<
C. is correct, because the question's asking for initial value, and this answer states that roberta had $50 before she started saving money. Which we can prove considering the graph starts between 60 and 40.
D. is wrong because clearly the graph shows us that the line does not begin at $0. D would only make sense if the line began at the origin of the graph, which is $0 and 0 weeks.
Your answer is C. I hope detailed explanation helped you on your online test!