Respuesta :

CD=50   DVD=40
5C+7D=530

C=D+10
C-D=10
Solve the system
5C+7D=530
5C-5D=50 (multiply by 5)
Subtract
12D=480
D=40
Substitute in any of the equations
C-D=10
C-40=10
C=50
58 cds and and 34 dvds