Converting Decimals to Fractions
If the decimal is in tenths (has only one digit after the decimal) the numerator of the fraction of that number is the number over 10. If the decimal is in hundredths (has two digits after the decimal) the numerator of the fraction is that number over 100, and so on.
Of course now you will need to reduce where possible.
You can double check that you’ve reduced correctly by dividing the numerator by the denominator. For example 99 divided by 200 is .495, which was the original decimal.
Converting Fractions to Decimals
Simply divide the numerator by the denominator. If you can’t use a calculator, this will normally involve some long division.
Since the numerator will normally be smaller than the denominator you will have to add a decimal and a zero before you can start dividing.
So the decimal of 7/12 (rounded to the nearest hundredth) is 0.58