This topic is in the 'Rational Numbers' section. Rational numbers are numbers that you can express as fractions made up of good old fashioned integers. So 3 is a rational number because it can be represented as 6/2 or just 3/1. Decimals that end or repeat are also rational numbers, since 0.25 is just 1/4 and 1.5 is just 3/2. And of course fractions like 1/2 or 5/6 are rational numbers too, because they are fractions made up of good old fashioned integers. So this section really deals with fractions and decimals, and contains tutorials that will help you convert between fractions and decimals, do arithmetic with fractions and decimals, and even solve equations containing fractions and decimals. There are numbers out there that can't be represented as fractions using good old fashioned integers, and those numbers are called irrational numbers. You'll learn more about those in the 'Real Numbers and Right Triangles' section!