Answer:
$240
Step-by-step explanation:
this would be solved using simultaneous equation
let c = cost of cds
d = cost of dvds
two equatiions can be derived from the question
5d + 9c = 285 eqn 1
5d + 5c = 225 equation 2
subtract equation 2 from 1
4c = 60
c = 15
substitute for c in eqn 1
5d + 9(15) = 285
5d = 150
d = 30
5(30) + 6(15) = 240
