What is 0.21212121.... as a fraction

if numbers repeat, it's problby divided by 9 or some multipule of 9 if 2 numbers repeat, it's probbalby divided by 99 like 0.abababababab=ab/99 so 0.21212121 21 repeats so it is 21/99 or 7/33

If we make the number equal to x... 0.21212121.... = x  multiply each side by 100 21.212121.... = 100x  remember that x is 0.21212121? we can subtract that now from 21.21212121, as well as x from 100. 21.212121... - 0.212121... = 100x - x  we are left with 21 = 99x 21 = 99x  simplify.... 7 = 33x  and divide! 7/33 = x Your answer is: 0.2121212121.... = 7/33