The graph below plots a function f(x):
graph of line segment going through ordered pairs 0,150 and 3, 0
if x represents time, the average rate of change of the function f(x) in the first three seconds is
answer for blank 1:

The average rate of change of a linear function is the slope of the line. Since we are given the following coordinates:
(0,150) and (3,0)
We can easily solve for the slope.
m = (y2 - y1) / (x2 - x1)
m = (0 - 150) / (3 - 0) = -50

Therefore, the average rate of change of the function in the three seconds is -50.