The question is asking about some proportionality between unknown quantities, so I would imagine they want to know if there is a proportionality between the TOTAL savings and the ammount saved each week.
The TOTAL savings can be expressed as:
TOTAL = 24 + 9 * x
(where "x" is the number of weeks)
so in such case, there is NO proportionality between the total saved and the amount saved per week, because there is a fixed term "24" interfering with the proportionality.
If it was:
TOTAL = 9 * x
then, there is a direct proportionality, but not in the case described.
In the case of the question about a leaky faucet dripping 12 ml every minute, there IS a PROPORTIONALITY between the TOTAL amount leaked and the time (in minutes)
TOTAL = 12 * time
so you see that there is a constant of proportionality (12) that relates the TWO quantities: Total leaked and time. In this case there is no extra added term as in the previous case.