How can I make an element's width equal to its neighboring element if the width cannot be fixed?

Question

css

The structure is like this:
<div>div+ul>li>img+span</div>

Answer 1

If the parent is set to display: flex; then child elements will default to the same height (smaller ones stretch to the tallest)

Answer 2

Flexbox will help solve the problem
https://css-tricks.com/snippets/css/a-guide-to-flexbox/