Two problems here- 1) find the total cost to the nearest cent, $100 dinner; 20% gratuity 2) find the total cost to the nearest cent, 12300 car; 5% sales tax

In both of these problems you are asked to find a percentage of another number and then add it to that number... In math

"is" means =
"of" means ×

1) In the first problem 20% of 100 is, means
20% × 100 =
.20 × 100 = $20

now add it to the cost of the meal.

100 + 20 = $120 (final cost)



2) In the second problem 5% of 12300 is, means
5% × 12300 =
.05 × 12300 = $615

add this to the original price for the final cost...

12300 + 615 = $12,915