42/59 as a percentage is 71.19%. This number tells you how much of a whole the fraction represents when it is expressed in hundredths. It is a handy way to compare the fraction with other values that are already in percent form.
The fraction 42/59 cannot be reduced any further, so it stays as a simple ratio of two whole numbers. When you see it written as 71.19%, you can quickly understand that it is a little more than seven‑tens of a percent, which is easier to picture than a messy fraction.
In everyday use, you might see 71.19% on a report card, a discount label, or a test score. Knowing the percentage helps you see the size of the part compared to a whole, without having to work with the original fraction.