The formula if help

You could use a nested IF() statement, the proper syntax would be something like:

IF({category} = "A", {total} * 0.5, IF(..., ..., IF(..., ...)))

Or you could use a SWITCH statement since you’re only looking at one field value.

SWITCH(
   {category},
   "A", {total} * 0.5,
   "B", {total} * 0.1,
   "C", {total} * 1,
)

Another way to write that SWITCH() function is to only use it to calculate the multiplier for {total}:

{total} * SWITCH(
   {category},
   "A", 0.5,
   "B", 0.1,
   "C", 1
)

thank you very much!
everything worked out

Glad to know that you got the answer you were seeking! If you would, please mark @Kamille_Parks’ comment above as the solution to your question (mine was just a variant of hers). This helps others who may be searching with similar questions. Thanks!