Formula to Add Two Cells Together with Seperate Formulas

Hello,
I need help with creating a formula. The result needs to be adding together two cells which have a multiplication for each. I want the results cell to have a blank result if it is zero. Here is what I have, but cell 890 and 891 are not adding their results together:
(note: cell 890 will be blank until I enter a value, and cell 891 will always have a fixed value).

Cell 890 and 891 will always be multiplied by the same value (9%), so maybe they should be added together first, then multiplied by 9%?

As this string now stands, the result cell is only showing the multiplication of cell 890

=IF(F890=0,"",(F890*0.09)+(F891*0.09))

Thank you

First off, I'm not sure your post meets forum rule #1 about vague titles. So you may get a ding from a moderator.
That being said, I created dummy data, plugged in your formula and it seems to be working whether I add them first or use the formula to do it. So what exactly is your problem? If they are not adding together maybe either cell is in as text or has something hidden like a carriage return?

Your formula worked for me but you might try putting another set of brackets on

=IF(c890=0,"",((c890*0.09)+(c891*0.09)))

Try this one

=IF(F890=0,"",SUM(F890*0.09,F891*0.09))

oops never saw the title

I tried your numbers in my data and blanked out your cell 890 and got the results you want.
If 29.71 in 890 and 5.5 in 891 I get 3.1689 in 892, if I null out 890 I get a blank in 892. Not sure what is different for you.

EDIT, and i get it whether I use your formula, the one from easyexcelanswers or the one from AlKey.

Being new to the forum you might not know that those who helped you (any or all) can be thanked by adding to their reputation at the bottom of their posts.
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Thanks for the feedback.

Thanks for the feedback!