To understand percents and how to calculate them it is most important that you remember that one whole is divided into one hundred little peaces. In this case, the whole is 75. So, the easiest way to find a certain percentage of a whole, is to divide it by one hundred and then multiply it with the percent that you want to find. So, to solve your question you have to divide 75 by 100, which gives you that one percent of 75 is 7.5, and then to find what 30 percent of 75 is, you multiply that one percent by 30, or 7.5 x 30, which gives you 22.5 - the wanted solution.
There are other ways of calculating percentage, but this is by far the easiest one for beginners to understand.
