GSHEP wrote:
adding 989.89 to 165.2
cells G23 H23
=G23+H23 in spreadsheet
answer should be 1155.09 calculation given is 1155.04

Probably an example of displayed v. actual precision of the numbers in
G23 and H23. The number displayed as "989.89" could be as small as
989.885. The number displayed as "165.2" could be as small as 165.15.
Their sum could be as small as 1155.035. The number displayed as
"1155.04" could be as small as 1155.035 or as large as 1155.0449...9.
So the values in G23 and H23 could be larger than their smallest
possible, and their sum could still display as "1155.04".

Increase the precision of the cells (Format Cells Number Number
Decimal Places), and you should the cause of the problem. You can usually avoid such anomalies by using ROUND() judiciously.