Answer:
Part a) The exact area of the sidewalk is 
Part b) The approximate area of the sidewalk is 
Step-by-step explanation:
we know that
The area of the sidewalk is equal to the area of the outer circle minus the area of the inner circle
Part a) Find the exact area of the sidewalk

![A=\pi [144-64]](https://tex.z-dn.net/?f=A%3D%5Cpi%20%5B144-64%5D)

Part b) Find the approximate area of the sidewalk
assume 
substitute

Answer:
5-12
=(-7)
Step-by-step explanation:
An arrangement of symbols denoting values, operations performed on them, and grouping symbols.
hope it helps
The Answer Would Be C He stops so his time stops then he starts again at the same speed
Answer:
There are 40 windows on the 10th floor
Step-by-step explanation:
Since we know one cube has 4 "windows" (each hole on its side not counting top and bottom) we can calculate that for each "floor" 4 more windows are added. So in other words, if "x" equals the amount of "floors" the equation for solving this would be 4x = # of windows.