Step 1 : Let's review the information given to us to answer the problem:
Price of the bill = $ 98.50
Percentage of the bill your dad wants to leave for the tip = 15-20%
Step 2: Let's calculate the 15% and the 20% of the bill
15% of the bill = 98.50 * 0.15
15% of the bill =$ 14.78 (rounding to the next cent)
20% of the bill = 98.50 * 0.2
20% of the bill = $ 19.70
Step 3: Now, let's add the 15% and the 20% we calculated on Step 2 to know how much your dad pays in total.
Total paid, including 15% tip = 98.50 + 14.78
Total paid, including 15% tip = You can calculate, Mike
Total paid, including 20% tip = 98.50 + 19.70
Total paid, including 20% tip = You can calculate as well
Step 4: Now you know how much in total your dad paid, either with 15% tip or with 20% tip