Answer:
$ 8874.11 after 5 years 
Step-by-step explanation:
  Each year it is worth 85 % of its value 
20 000 ( .85)^5 = 8874.11
 
        
             
        
        
        
Answer:
Optical axis
Step-by-step explanation:
Optical axis is the rotational symmetry axis of the surfaces.
A line with a certain degree of rotational symmetry is called as the optical axis in an optical system.
It is the straight line that passes through the geometric center of the lens and joins two curvature centers of its surfaces.
It is also called as the principal axis.
 
        
             
        
        
        
Step-by-step explanation:
Let the length be L.
Let the breath be B.
So, we are given that
length of a rectangle is 7 inches greater than three times its width .
So, according to the Question,
L = 7+ 3B.
So, we know that:-
Area = Length× Breadth.
So, it will be 
B × (7 + 3B) = Area.
So,
3B² + 7 is an expression to represent its area.