2 pack of batteries cost x dollars.
Therefore 1 pack of batteries costs x/2 dollars
Let n packs of batteries be purchased for $5.00
Then 1 pack of batteries costs 5/n dollars
Equate the cost of 1 pack of batteries.
x/2 = 5/n
Cross multiply.
nx = 10
n = 10/x
Answer:
The number of packs of batteries is 10/x.