Average with specific conditions

Several different ways to accomplish this, report, page or visual level filters, using AVERAGEX with an appropriate FILTER clause. If you want this to be dynamic, that will take a little more work but could be accomplished using a temporary table and IN most likely. But, that would need sample data to be specific. Please see this post regarding How to Get Your Question Answered Quickly: https://community.powerbi.com/t5/Community-Blog/How-to-Get-Your-Question-Answered-Quickly/ba-p/38490