How do i change a decimal in to a fraction .333

Well, with recurring numbers, like .333333..., instead of the fraction being /100, it's actually out of 99 surprisingly. 

So in that case, it turns into 33/99

If it were 0.6667,
it would be

66/99

For non-repeating decimal
0.333 = 333/1000

for repeating decimal 0.333...
let x = 0.333... (1)

multiply x with 10^n where n=number of unduplicated repeating digit.
in this case only 1 digit which is 3 so we multiply with 10^1 or 10
so 10x = 3.333... (2)

now
(2)-(1). 10x - x = 3.333... - 0.333...
9x = 3
x = 3/9 = 1/3 this is the fraction of 0.333...