As a couple of examples:
.33333.......
let 'x' = .3333333.....
then 10x = 3.33333.....
subtract 'x' fro 10x 3.3333.....
- .3333....
____________
9x = 3.0 Solve for 'x'
x = 3/9 = 1/3
Another one:
.8989898989.......
let 'x' = .8989.....
then 100x = 89.8989..... (not that we have to use 100x in this example because there are TWO repeating digits)
then 100x - x
89.8989........
- .8989.......
____________
99x = 89. Solve for 'x'
x = 89/99
Do you have SPECIFIC examples of which you need help ???