Mental math refers to performing calculations in your head without the use of calculators or paper.

Break down the numbers into smaller, manageable parts. For example, to subtract 3999 from 6000, think of it as 6000 - 4000 + 1.

0.29

Align the decimal points and subtract: 3.81 - 2.79 = 1.02.

'Less than' indicates a subtraction operation. For example, 'ninety-nine less than two hundred and eighteen' means 218 - 99.

When adding time, add the minutes first, and if they exceed 60, convert to hours. For example, 9:55 AM + 18 minutes = 10:13 AM.

Addition combines numbers to find a total, while subtraction finds the difference between numbers.