Final answer:
To find the total bill after adding the tip, multiply the dinner bill by the tip percentage and then add the tip amount to the dinner bill.
Step-by-step explanation:
To find the total bill after adding the tip, we first need to calculate the amount of the tip. In this case, the dinner bill is $81.50 and they want to leave an 18% tip. To find the tip amount, we multiply $81.50 by 18% (0.18) to get $14.67.
Next, we add the tip amount to the dinner bill. $81.50 + $14.67 = $96.17. Therefore, the total bill after adding the tip is $96.17.