A decimal is a number divided by 10: 0.x = x/10, whatever the x number might be. If the "decimal" has more digits, then is divided by 100, 1000, and so forth: 0.0y = y/100, 0.00z = z/1000
So the trick for a mixed number to be written as a decimal is first to write the mixed number as a fraction, then, when you have a fraction, you need to make the denominator of the fraction equal to 10, 100, 1000, 10000, etc, and then you have it done.
For example, 4/25 as decimal is:
(4/25) = (4*4)/(25*4)
= 16/100, and that is = 0.16
