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 solution must be larger than 9, because the answer is h=10
Expand and simplify
(x-3) (x-3) +2(x-3) -8=0
(x-3+2)(x-3)-8=0
(x-1)(x-3)-8=0
x^2 -4x +3-8=0
x^2 - 4x -5=0
x^2 -5x +x-5=0
x(x-5)+x-5=0
(x+1)(x-5)=0
x= - 1, 5
