Portion of the Whole
A percent is secretly just a fraction where the denominator is 100. However, we can also think of a percent as telling how much a part is of the whole. For example, if 75% of all charts used to demonstrate percents are in the form of pie charts, you could demonstrate that by filling in 3/4 of a pie chart. Ooh, we hope that doesn't skew our data.
To figure out what percent a is of b, write the fraction a/b and convert it into a decimal. Then change the decimal to a percent.
What percent is 6 of 24?
6/24 = 1/4 = 0.25 = 25%
So if you watch Mad Men for 6 hours, that's 25% of your day you've spent watching TV. Oof.
The question could also be phrased, "What percent of 24 is 6?" The number after the word "of" is the whole, and the other number is the part. Don't always assume the bigger number is the whole, however. You might also be asked, "what percent of 6 is 24?" The answer to that one would be 400%. Which is definitely too much television.