18/39 as a percentage is 46.15%. This number tells you how much of a whole the fraction represents when you look at it on a scale of 100.
The fraction 18/39 can be reduced to its simplest form, 6/13, which still gives the same value. Whether you write it as 18/39, 6/13, or 46.15%, the amount stays the same—it’s just different ways to show the same part of a whole.
In everyday situations, you might use the percentage to compare parts of a group, such as saying that 46.15% of the class prefers pizza over burgers. The percentage makes it easy to understand and communicate the size of the part without dealing with fractions.