In Problems 1-4, write the given decimal as an infinite series then find the sum of the

Question:

In Problems 1-4, write the given decimal as an infinite series then find the sum of the series, and finally, use the result to write the decimal as a ratio of two integers (see Example 2)?
1. 0.22222...
2. 0.21212121...
3. 0.013013013...
4. 0.125125125