How to correctly place 3 columns in a block?

Question

css

I'm racking my brains on how to properly make 3 responsive columns of equal width.
There is a basis in which it needs to be implemented. My attempts were unsuccessful (it will go out of the block, then move down ...)
Here is the basis: https://codepen.io/Energy2/pen/mjqeZX

Answer 1

https://codepen.io/oxythres/pen/YjEwpa