Product Landing Page boxes not distributing correctly

HTML-CSS
#1

Hello, world.

I’m kind of finishing the Product Landing Page project, but the three boxed at the bottom aren’t distributing their width evenly. At least I want them to be like the example.

Codepen link

Also, when the media query activates, the width of the three boxes just breaks.

#2

Fixed. width: 100% to the parent element.

#3