80p = 80 cents
£1.50 = $1.50.
(changing the signs, that's it)
So if a small bottle is half the size of a large bottle, and is 80 cents.
Amir buys 4 bottles, so 0.80 * 4 = 320 = $3.20.
Now 4 small bottles is the same as 2 large ones, so if he bought 2 large bottles: $1.50 * 2 = $3.00.
$3.20 - $3.00 = 0.20 cents.
Amir would've saved 0.20
P.S. What is "p" in European money
