The question is incomplete and there is no specific topic mentioned. However, based on the search results, here is a general explanation of how to calculate percentages:

• A percentage is a way of expressing a number as a fraction of 100.
• To calculate a percentage, divide the part (the smaller value) by the whole (the larger value), and then multiply the result by 100.
• For example, if you have 50 apples and you want to know what percentage of them are red, and 20 of them are red, you would divide 20 by 50 to get 0.4, then multiply by 100 to get 40% .
• Percentages are used in a wide variety of contexts, from calculating discounts and taxes to measuring changes in stock prices and economic indicators.
• Percentages can also be used to compare two numbers or represent a portion of a whole.

In conclusion, to calculate a percentage, divide the part by the whole and multiply by 100. Percentages are used in various fields to represent a portion of a whole or to compare two numbers.