To calculate the total amount that Oliver paid, we need to follow these steps:
- Calculate the tax: The tax is 5% of the subtotal, which is \(0.05 \times xx\).
- Calculate the total bill including tax: This is the subtotal plus the tax: \[ \text{Total bill} = xx + (0.05 \times xx) = xx + 0.05xx = 1.05xx \]
- Calculate the tip: The tip is 16% of the total bill. Thus, we have: \[ \text{Tip} = 0.16 \times (1.05xx) = 0.168xx \]
- Calculate the total amount paid: This is the total bill plus the tip: \[ \text{Total amount paid} = (1.05xx) + (0.168xx) = 1.05xx + 0.168xx = 1.218xx \]
So, the expression in terms of \(xx\) that represents the total amount Oliver paid is: \[ \boxed{1.218xx} \]