You're letting x = 0.325325325…, which means
1000x = 325.325325325… (or 325.325, but pretend the underline is actually an overline)
Then the next box you'd fill in with 0.325325325… (or 0.325).
Subtracting these, you have
1000x - x = 325.325325325… - 0.325325325…
999x = 325
Finally, solving for x gives
x = 325/999