If the fix bases (A2) are those 3, the fee is calculated by:
=A2*(IF(A2>75000;12,5%;IF(A2>25000;17,5%;22,5%))
That means that IF the amount is over 75000, then apply 12,5%; if it's not (means it's less) then check if is more than 25000; if it is, apply 17,5%, if it's less than 25000 then apply 22,5%.
In all cases, you have to indent IF formulas (you can indent up to 7 IFs in the same bracket) starting from the highest value you need to check. Check attachement!