Final answer:
To calculate a 15% tip on a $136.20 bill, convert 15 percent to a decimal (0.15) and multiply it by the amount of the bill, which results in a tip of $20.43.
Step-by-step explanation:
If a guest check total is $136.20 and a server earns a 15 percent tip, the correct tip amount is found by converting the percent to a decimal and multiplying it by the cost of the meal. Firstly, convert 15 percent to a decimal, which is 0.15. Then multiply this decimal by the total amount of the bill to calculate the tip:
0.15 × $136.20 = $20.43
Therefore, the correct tip amount for the server would be $20.43, which corresponds to option B.