What does the initial value mean for this function?

Roberta saves $10 each week.

After 4 weeks, Roberta has $90.

Roberta had $50 before she started to save money each week.

Roberta had no money until she started to save $10 a week.

She saves 10 per week ... after 4 weeks, she had 90

so if she started with nothing, after 4 weeks she would have 40 ... but for her to have 90, she would have had to have started with (90 - 40) = 50.

Think about it ... she starts with 50 ... and then saves 10 for 4 weeks giving her 40 ... and now she has 40 + 50 = 90

so ur answer is : Roberta had $ 50 before she started to save money each week