Difference between periods from selected months and years

[Anonymous]

Hi,

I need help getting the percentage diference between periods from selected months and years based on x amount per year. 

For example: 

Jan - Jun          2021       2022        X/Dec
Total X             163         38            -77% (How can I get this in BI.)
Avg/mo           27.2        6.3           -77% (How can I get this in BI.)

Any help will be appreciated. 

[daXtreme]

It's rather not possible to give you a formula witout any context. At a minimum one needs to know at least some broad outline of what your model looks like...