Closed and Created incidents report

Content

Hi Gurus,

We want to show the report on last 3 months, how many is created on particular month and how many closed on particular month. 

I have used 

date_group(incidents.created,'YYYY-MM') function in one column

count(incidents.created) function in one column

count(incidents.closed) function in one column

What should be the filter condition?

We want to know the number of incidents closed on particular month regardless of creation month. I could not use created field in my filter.

Thanks,

Mohan