What is the proper way to adjust the width of a div within a flexbox?

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To adjust the width of a div within a flexbox, you should use the "flex-basis" property with a specific value. For example:

.container {
  display: flex;
}

.item {
  flex-basis: 50%; /* adjust the width to 50% */
}

You can also use the "flex-grow" and "flex-shrink" properties to adjust the width of the div based on available space and content size.