Let's denote the price of each CD before tax as \( x \).
Since Teresa bought 4 CDs, the total price before tax for all the CDs would be: \[ 4x \]
Each CD has a sales tax of $0.80, so for 4 CDs, the total sales tax is: \[ 4 \times 0.80 = 3.20 \]
Now, we can write an equation for the total amount Teresa paid, which includes the price of the CDs plus the sales tax: \[ 4x + 3.20 = 46.40 \]
Next, we can isolate \( 4x \) by subtracting the sales tax from the total amount: \[ 4x = 46.40 - 3.20 \] \[ 4x = 43.20 \]
Now, we can solve for \( x \) by dividing both sides by 4: \[ x = \frac{43.20}{4} = 10.80 \]
Thus, the price of each CD before tax is: \[ \boxed{10.80} \]