Marking best answer as brainliest :))

-25

Step-by-step explanation:

You must first pick two points.  I picked the points of (4, 400) and (8, 300).  You can pick different points and still get the right answer.

Subtract the y's and the x's.  Divide the difference of y by the difference of x.

400 - 300 = 100

4 - 8 = -4

100/-4 = -25

The slope, or rate of change, is -25.

he spend 5.1 minutes chatting with his friends.

step-by-step explanation:

2/5+1/2=9/10

6/1-9/10=5.1

step-by-step explanation: yes