To find a percentage of anything divide the number you want to find the percentage of and then times it by the percentage. Eg 260 divided by 100 equals 2.6 then times it by 15 so 15 percent of 260 will be 39.
Percentages are just another term for a figure of measurement. Each percentage point is one tenth of the whole. Or .10 of X (the total amount/#/measurement). So if you need 15 percent of 260 it would look something like -
15 (total percentage) x .10 = .150 or .15
.15 x 260 = final answer
this can also be noted in other ways. For instance all are equal - 15/100 = .15 = 1.5/10 = 15%
Math is a language and the grammar of it can be manipulated, but the answer is always the same...have fun with it.