Answer:
7 people, 7 walls, 48 minutes
Each person paints 1 wall in 48 minutes
20 persons, 20 walls
Each person can paint 1 wall in 48 minutes so it will take 48 minutes.
Answer:

=====================================================
Work Shown:

You could expand terms out and simplify, but I think it's more handy to leave it in this form so you can easily spot the center and radius from a glance.
Plug the points into the equation.
Ex. y=3x-5
(X,y)
1. (5,10): 10=3(5)-5
15-5=10; point 1 is valid
-1=3(-2)-5
-1=-6-5
-1 does not equal -11
Point 2 is not valid
Same process for letter B
It is biggest to smallest I presume
Answer:
c = 64
Step-by-step explanation:
Given
x² - 16x + c
To complete the square
add ( half the coefficient of the x- term )² to x² - 16x
x² + 2(- 8)x + 64
= (x - 8)²
Thus
x² - 16x + 64 = (x - 8)² ← a perfect square
with c = 64