Three column preview card component using Flexbox

I found the buttons a little bit difficult while building the project, specifically their width. I used a percentage measurement that seemed to go well as far as responsiveness, but is there a best practice?

I found this to be a fairly straightforward exercise in Flexbox, which I seem to be getting the hang of. I also changed the original orange color to a darker hue because an accessibility check yielded a low contrast warning.