Answer:
Step-by-step explanation:
Let
s -----> the number of stamps
w ----> the number of weeks
we know that
The linear equation that represent this situation is
----> equation of the line into slope intercept form
where
the slope m is equal to 
the y-intercept b is equal to
---> (the initial value)
The fourth one should be the correct answer
((5x2)+5.5+(6x3)+6.5+(7x5)+(7.5x4)+(8x4))/20
137/20
= 6.85
A constant because it a number
y = 1/2x + 3
change x and y
x = 1/2y + 3
now find the value of y and that is inverse function
x - 3 =1/2 y
y = 2x- 6
f-(x) = 2x - 6
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for both domain : ( - ∞ , + ∞ )
range f (x) : ( - ∞ , + ∞ ) - { 0 }
range f-(x) :( -∞ , +∞)