$14 meal; 20% tip me on this it is mathematics

The tip would be $2.80 because it is 20% of the $14 meal

First, convert the 20% 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 20%) by 100%.So, the conversational term "20%" becomes 20% / 100% = 0.20 in terms of a real mathematical number.
Second, you need to find out what 20% of your $14 meal cost is.This is always done by multiplying 0.20 by $14.00, or

0.20 x $14.00=$2.80.
So, the amount of tip you are going to leave is $2.80.

This makes the total cost of your meal (to write on your charge slip or other payment)

$14.00 + $2.80 = $16.80.

Quick tip calculation for 15% tips:

If you're leaving the standard 15% tip, here's a quick and easy way to calculate it in your head, at the table in the restaurant, without embarassing yourself by scribbling all over the back of a receipt or getting out a calculator:
15% is 10% + 5% (or 0.15 = 0.1 + 0.05, dividing each percent by 100). Thinking about it this way is useful for two reasons. First, it's easy to multiply any number by 0.1; just move the decimal point left one digit. For example, 75.00 x 0.1 = 7.50, or 346.43 x 0.1 = 34.64 (close enough). Second, 5% is exactly half of 10%. So here's how this quick and easy method works:
Take the total cost of your meal, $14.00 and multiply it by 0.1 by sliding the decimal to the left one digit to get $1.40 (you can do this in your head at the table). $1.40 is 10% of your meal cost. But the proper tip to leave is 15% (you need to throw in another 5%).

The additional 5% is just half of the 10% amount. What is half of $1.40? About $0.70. (Finding half of a number is also something you can do in your head at the table.) So, the total tip to leave is the 10% amount PLUS the 5% amount (for a 15% tip) or $1.40 + $0.70 = $2.10 .

The general rule here is:

Find the number that results from sliding the decimal point of the meal's cost left one digit,
and add on another half of this number.

That's your tip!

This is the graph x=1