
Mike D. answered 10/26/20
Effective, patient, empathic, math and science tutor
Suppose the price is $ x
Then she can purchase 12/x packs at the first store
At a discount store the price is $ (x - 0.50) per pack
So for $ 12 she can purchase 12 / (x-0.50)
So 12/x + 2 = 12 / (x-0.50)
12/x = 12 / (x-0.50) - 2 = (12 - 2x + 1) / (x - 0.50)
So 12 (x-0.50) = x (12-2x+1)
12x - 6 = 12x - 2x2 + x
2x2-x-6 = 0
(2x+3) (x-2) = 0
x = 2
So $ 2
Check.
For $ 12 she can buy 6 packs
If price is $ 1.50 she can but 12/1.5 = 8 packs = 6 + 2

Mike D.
You could also try guess and check here. Try x = 1, 2, 3, ...... and see what works10/26/20