Card to display last 5 days average

I have a page with date slicers to select year(s), month(s) and YearWeeks, and my line chart is working great.

Now I want to add a Card next to the line chart that displays the average value of the last 5 days that are currently displayed in the line chart.

How do I approach this?  Is it done via a measure, a column or a combination?

Thank you.