Data card value based on filter selection

Hi folks,

I need to create a data card value based on a selected filter. The table has 100 rows. One column is employees and the filter column named AgeGroup is a text string. there are 2 ageGroup values. One is 20-25 and the other is 25-30. there are 15 agegroup entries of 20-25 and 85 entries of agegroup 20-25.

Can someone provide guidance on how I might construct the DAX measure that returns a percentage of any selected agegroup?

TIA