When you divide a number by 10^n (i.e. 1 followed by n zeroes), you move the decimal point separator n places to the left (assuming that integers have the decimal separator at the end, as in 2 = 2.0).
So, the first option is to divide 18 by 100. So, we start from 18=18.0 and move the separator two places to the left:

The second option is to divide 8 by 10. So, we start from 8=8.0 and move the separator one place to the left:

The third option is to divide 18 by 10. So, we start from 18=18.0 and move the separator one place to the left:

So this is the correct option.