This is actually very simple once you know it!
To find the decimal percent equivalent, simply divide the numerator by the denominator, and then you multiply the answer you get from dividing the numerator by the denominator by 100!
Words, words, words... let's look at an example:
Let's say you want to turn $${\frac{{\mathtt{1}}}{{\mathtt{10}}}}$$ into a percentage. Just take the numerator (1) and divide it by the denominator (10) like this: 1 / 10 = 0,1.
Alright, we've got 0,1. That's a decimal. I wanted a percentage. Well then! Let's continue, multiply the value you got, which is 0,1, by 100 like this: 0,1 * 100 = 10. You got it! 10! 10%!
What about something more complicated? Like $${\frac{{\mathtt{345}}}{{\mathtt{890}}}}$$? Same principle! 345/890 = 0,3876404494382022. 0,3876404494382022 * 100 = 38,76404494382022. Answer: 38,76404494382022%.
Phew, let's hope I copy-pasted all those values correctly.
EDIT: Turns out I didn't. Fixed. :)
