Answer:

Step-by-step explanation:
Let
y -----> gallons of water remaining in the barrel
x-----> number of minutes elapsed
we know that
Water leaks out of the barrel at a rate of 1 gallon every 10 minutes
so

The linear equation that represent this situation is

The graph in the attached figure
It will be 4f-30. Using substitution, you get (-8f-12) + (12f-18). Adding this together you get -8f-12+12f-18. Then you add -8f and 12f to get 4f, and add -12 and -18 to get -30.
The multiplier is 1 + (percentage increase) = 1.0013.
_____
It make no sense to talk about percentage changes in temperature. Just sayin'.