Its basic division really. The easiest way to think of it is how many times can 3 fit into 12 three fits into 12 four times in fraction that's 1/4 or 1 over 4. Just like the quarter (United States quarter) each one is 25 cents and you need 4 of then to make 1 US dollar or 100% so each group of three is 25 percent. This under standing could work with a variety of numbers 5 is what percent of 20 or 7 is what percent of 28 if it comes in 4s each is 25%. Hope this helps.
