Okay so using the formula part/whole = percent/100 youd substitute in your data.
N/ 9900= 13/100
now you would cross multiply this will give you
100n=128700
now you need to divide by 100 on both sides to find out what your N is. This will tell you what 13% of 9900 is.
N=1287
Now to find out what 13% less than 9900 is you need to subtract your N [1287] from 9900
your answer will be 8,613 :)
