Answer:
-Exponential Decay
-Decay factor is (1-0.05)
Step-by-step explanation:
-Given that the number decreases by a defined rate each year from the initial size by 5%,
-This is an exponential decay function of the form:

Where:
is the quantity/size after time t
is the initial size
is the rate of decay
-Our function can the be written as

Hence, the decay rate/factor is 0.05
#Alternatively
The exponential decay can be of the form:

Where:
y is the size at time x, a is the initial size, x is time and b is the decay factor.
b is of the form 

Hence, the decay factor is (1-0.05)
The distance (d) between two points (x1,y1) and (x2,y2) is given by the formula
d = √ ((X2-X1)2+(Y2-Y1)2)
d = √ (-400--800)2+(300-200)2
d = √ ((400)2+(100)2)
d = √ (160000+10000)
d = √ 170000
The distance between the points is 412.310562561766
The midpoint of two points is given by the formula
Midpoint= ((X1+X2)/2,(Y1+Y2)/2)
Find the x value of the midpoint
Xm=(X1+X2)/2
Xm=(-800+-400)/2=-600
Find the Y value of the midpoint
Ym=(Y1+Y2)/2
Ym=(200+300)/2=250
The midpoint is: (-600,250)
Graphing the two points, midpoint and distance
P1 (-800,200)
P2 (-400,300)
Midpoint (-600,250)
The length of the black line is the distance between the points (412.310562561766)
A fraction. I.E. : 6 has 36 parts (6 parts per one) If you took 2 out of the six parts away you would get 32/6 or 5 2/6 (2/6 could be simplified to 1/3)