Let, cost of 1 hot dog and 1 drink is x and y respectively.
Carl bought 4 hot dogs and 6 drinks and paid $23.80.
4x + 6y = 23.80 ....1)
Susan purchased 4 hot dogs and 2 drinks and was charged $15.40.
4x + 2y = 15.40 ....2)
Subtracting equation 2 by 1, we get :
(4x + 6y) - (4x + 2y) = 23.80 - 15.40
4y = 8.4
y = $2.1
4x + 6×2.1 = 23.80
4x = 23.80 - 12.2
4x = 11.6
x = 2.9
Therefore, the cost of 1 hot dog and what is the cost of 1 drink is $2.9 and $2.1 respectively.
Hence, this is the required solution.