To convert a fraction to a percentage, you multiply the fraction by 100. So for 3 out of 10, you would calculate it as follows:
(3 / 10) * 100 = 30%
This means that 3 out of 10 is equal to 30%. In other words, if you had 10 items and 3 of them were a certain category, that category would represent 30% of the total items.