The rate of change of the linear relationship is -1.
Explanation:
It is given that there is a linear relationship between all these points, these points lie on a straight line.
The equation to find the slope passing through two points
and
is given by

Substituting the points
and
, we get,

Thus, the slope is -1.
Thus, the rate of change of the linear relationship is -1.
The barrel had 20 liters....after 24 hrs, it had 14 liters......that means in 24 hrs, it leaked (20 - 14) = 6 liters....so it is leaking 6 liters every 24 hrs
liters / hr = 6/24 = 0.25.....so it is leaking 0.25 (or 1/4) liters per hr