I think it’s the second one because The formula would be
x=
2a
−b±
b
2
−4ac
-5n + 8 = -7
-5n + 8 - 8 = -7 -8
-5n = -15
-5n/-5 = -15/-5
n = 3
The calculations for 2, 4, 8 year can be derived as follows,
For simple interest:
S.I = 
P= principle
T= Time
R= Rate
For 2 year;
S.I =
= $224
Amount = $2224
For 4 year;
S.I =
= $448
Amount = $2448
For 8 year;
S.I =
= $896
Amount = $2896
4 units left : subtract 4 from each x coordinate
3 units down : subtract 3 from each y coordinate
that is how i remember it