The music store will charge $5 for a yearly membership.
Explanation:
Let the cost per vinyl album be 'a'
Let the yearly membership cost be 'b'
Given that,
4a + b = 35
7a + b = 57.5
9a + b = 72.5
We can take any 2 equations from the above,
(4a + b = 35 ) - (7a +b =57.5)
4a + b - 7a - b = 35 - 57.5
-3a = -22. 5
3a = 22.5
a = 7.5
The cost of each vinyl album is $7.5
4a + b = 35
4(7.5) + b = 35
30 + b = 35
b = 35 - 30
b = 5
The cost of the yearly membership is $5
The music store will charge $5 for a yearly membership.