If you want the string of digits "285714" to repeat forever, then let
x = 0.285714 285714...
The spaces are there to help separate the blocks but just imagine thats all one decimal
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Multiply both sides by 1,000,000 so that you move the decimal point over exatly 6 spots to the right
1,000,000x = 285714. 285714 285714...
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Now subtract the two equations
1,000,000x-x = (285714. 285714 285714) - (0.285714 285714...)
999,999x = 285714
x = 285714/(999,999)
x = (2*142857)/(7*142857)
x = 2/7
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So, x = 2/7 = 0.285714 285714...
where the block "285714" repeats forever. Remove the spaces in the number above if needed.