Step-by-step explanation:
x = price per video game
y = price per CD
164 = 5x + 3y
and then we know
x = y + 12
now we can use this as substitute in the first equation :
164 = 5(y + 12) + 3y = 5y + 60 + 3y = 8y + 60
104 = 8y
y = $13
x = y + 12 = 13 + 12 = $25
so, each CD costs $13.