can someone help me I don't understand

Answer:
(a) 165 m/min
(b) 107.14m/min
Step-by-step explanation:
The slope of the distance time graph gives speed.
Here, the speed of the segment A is
[tex]v_A= \frac{900-0}{4-0}=225 m/min[/tex]
The speed of segment B is
[tex]v_B= \frac{1500- 900}{14-4}= 60 m/min[/tex]
(a) The change in speed is
= 225 - 60 = 165 m/min
(b) The average speed is defined as the ratio of total distance to the total time.
So, the average speed is
[tex]= \frac{1500}{14}= 107.14 m/min[/tex]