Write a real world problem that involves a percent then model the percent used in the problem

You go to a restaurant and your bill is $35.00. Your service was excellent so you leave a 20% tip. What was the total amount paid for the bill including the tip?

10%=$1 for every $10
15%=$1.50 for every $10
20%=2% for every $10

10% of the bill would be $3.50(move the decimal to the tens place)
15% of the bill would be $5.25( halve the 10% and add it to the original 10% tip; $3.50+$1.75)
20% of the bill would be $7.00(double the 10% tip)

Ok but uh what do you need with?