Let
x-------> total number of CD
we know that
1) Jake's mom purchased [tex]40\%[/tex] of the copies in the store.
2) Jake's mom has [tex]80[/tex] copies of the CD
3) [tex]80[/tex] copies of the CD represent [tex]40\%[/tex] of the copies in the store
so
[tex]40\%=\frac{40}{100} =0.40[/tex]
[tex]x*0.40=80[/tex]
solve for x
Divide by [tex]0.40[/tex] both sides
[tex]x*0.40/0.40=80/0.40[/tex]
[tex]x=80/0.40[/tex]
[tex]x=200\ CD's[/tex]
therefore
the answer is
[tex]200\ CD's[/tex]
