You want to leave a 15% tip on a meal that cost $15.77.
First, convert the 15% to an actual number that can be used in a calculation. For percents,this is always done by simply dividing the percent (in this case 15%) by 100%.So, the conversational term "15%" becomes 15% / 100% = 0.15 in terms of a real mathematical number.
Second, you need to find out what 15% of your $15.77 meal cost is.This is always done by multiplying 0.15 by $15.77, or
0.15 x $15.77=$2.37.
So, the amount of tip you are going to leave is $2.37.
This makes the total cost of your meal (to write on your charge slip or other payment)
$15.77 + $2.37 = $18.14
$18.14 is your answer