So the mixed number rule should help. Since we have a whole number, which is 1, then it stays like that. The "12121212121..." means that it repeats the number, 12, many times, meaning that the denominator is 99 (12 = 99 for the denominator.) We would get 12/99, but the thing is that we can simplify this fraction (we divide the numerator and the denominator 3 times for this fraction), giving us 4/33.
Hope this helped!
Nate
