45/100 x 800 = 360

Some facts about the question;

percentage

In mathematics, a percentage is a way of expressing a number as a fraction of 100 (per cent meaning “per hundred”). It is often denoted using the percent sign, “%”. For example, 45 % (read as “forty-five percent”) is equal to 45 / 100, or 0.45.

Word and symbol

Main article: Percent sign

In British English, percent is usually written as two words (per cent, although percentage and percentile are written as one word). In American English, percent is the most common variant (but cf. per mille written as two words). In EU context the word is always spelled out in one word percent, despite the fact that they usually prefer British spelling, which may be an indication that the form is becoming prevalent in British spelling as well. In the early part of the twentieth century, there was a dotted abbreviation form “per cent.”, as opposed to “per cent”. The form “per cent.” is still in use as a part of the highly formal language found in certain documents like commercial loan agreements (particularly those subject to, or inspired by, common law), as well as in the Hansard transcripts of British Parliamentary proceedings. While the term has been attributed to Latin per centum, this is a pseudo-Latin construction and the term was likely originally adopted from Italian per cento or French pour cent. The concept of considering values as parts of a hundred is originally Greek. The symbol for percent (%) evolved from a symbol abbreviating the Italian per cento.

Grammar and style guides often differ as to how percentages are to be written. For instance, it is commonly suggested that the word percent (or per cent) be spelled out in all texts, as in “1 percent” and not “1 %.” Other guides prefer the word to be written out in humanistic texts, but the symbol to be used in scientific texts. Most guides agree that they always be written with a numeral, as in “5 percent” and not “five percent,” the only exception being at the beginning of a sentence: “Ninety percent of all writers hate style guides.” Decimals are also to be used instead of fractions, as in “3.5 percent of the gain” and not “3 ½ percent of the gain.” It is also widely accepted to use the percent symbol (%) in tabular and graphic material. Variations of practically all of these rules may be encountered, including in this article; the only really fast rule is to be consistent. It is important to know what method of solving the problem you would use.

multiply that by 4 you get 320

5% of 80 is 40

add that to 320 you get 360

& the person who posted above me is wrong….

320 + 40= 360, not 380

the answer is 360