"Operand data type varchar is invalid for sum operator" error when trying to add

Cognos 8 Business Intelligence Report Studio
1

I have a query calculation:
[Business Logic View].[Workorder].[ACTLABCOST]+[Business Logic View].[Workorder].[ACTSERVCOST]+[Business Logic View].[Workorder].[ACTTOOLCOST]+[Business Logic View].[Workorder].[ACTMATCOST]

And I’m receiving that error when I try to run the report. The data type of those fields is actually ‘decimal’ not ‘varchar’ so I’m not sure why I’m still receiving this error