So the fraction $\frac12$ is equivalent to the 0.5 which is its decimal representation. That works for any fraction. Simply divide the denominator into the numerator and we get the resulting decimal.
Suppose we had a decimal and we wanted to convert it to fraction. That's a little bit easier. To convert the decimal 0.452 into a fraction, start with your pencil under the decimal point and draw a line horizontally across until it just passes the last number which in this case is 2. Under the decimal, put a number 1 and put 0's under the digits. Finally drop the leading 0, and get rid of the decimal point from the original number and our result is the fraction equivalent. So our resulting fraction is $\frac{452}{1000}$.