Question 639250
X as CDs cost 7.5 ea
Y as CDs cost 6.5 ea

7.5*X+6.5*Y=82
X+Y=12

If all 12 CD are 7.5 ea,
7.5*X+7.5*Y=90
Minus [7.5*X+6.5*Y=82]
Y=8
X=4