Answer :
Let, fee and amount of money per minute used is P and m respectively.
Also, monthly fee is given by C.
The linear equation is given by :
[tex]P=mx + c[/tex]
( Here, x is the number of minutes )
Putting both the conditions in above equation, we get :
[tex]205 = 370m + c[/tex] .....1)
[tex]405=770m +c[/tex] .....2)
Subtracting 2 by 1, we get :
(770 - 370)m = 405-205
400m = 200
m = $0.5 .
So, c = 205 - 370×0.5
c = $20 .
Therefore, monthly fee and fee per minute used is $20 and $0.5 respectively.
Hence, this is the required solution.