Answer:
The first question is -1.25
I don't know the answer to the second one, but i think it's +2.5
Explanation:
y is the same as fx
the rate of change is also the slope, and as x increases by 4, y decreases by 5, slope is change in y / change in x, so -5/4 = -1.25, every hour the candle's length decreases by 1.25.