A fraction is just a short way to write a division problem. When you see a fraction, it just means "the top number divided by the bottom number". The fraction in your question means "49 divided by 12".
When you actually DO the division, the answer you get is usually in decimal form.
So go ahead. Pull out your calculator or your pencil, divide 49 by 12, and there you'll see the decimal form of the fraction, staring up at you.