How to resize img src in HTML <style>?

Here I am:

<style>
 h1 {
    color: orangered;
   font-family: rockwell;
  }
  img {
    size: 80px;
flex-fit: (50%);
self-justify: center;
}
 <img src="https://1.bp.blogspot.com/-wDOg0ZdTR0U/UAQ-50kYA8I/AAAAAAAAIRY/hPzQ8NQrv3k/s1600/k08+-+Un+rose+et+un+rouge.JPG"
</img>

Thanks… I will have a look on this Responsive Web Design curriculum again.

There are no such properties. For what you have as flex-fit you may be thinking of flex-basis, or at least that is a property that would let you set a presentage value. For self-justify you may be thinking of justify-self, however that doesn’t work with flexbox, only align-self works with flexbox.