C: B:
3 0
6 9
9 18
12 27
All you had to do was plug in the value for c or b and solve. You can tell this is most likely correct because you see patterns for both variables. C is going up by threes, while b is going up by nines.
They definitely can be positive they can be negative and they can have an absolute value but I would choose they both can be positive and negative
D) Requires a linked bank acount
I believe 24 months because by then you will have accumulated $720 hope it helps