Answer:
Independent variable (x in 2D cartesian) = t (time)
Dependent variable (y in 2D cartesian) = p (battery power)
The independent variable is time.
The dependent variable is battery power.
Time is independent because it cannot be controlled.
Battery power is dependent because it can be controlled.
Since t is in hours,
The battery power begins at 100% and decreases 5% each hour.