put divs on ends diplay flex code example
Example 1: css flex center
display: flex;
align-items: center;
justify-content: center;
Example 2: flexbox align right and left
.primary-nav {
display:-webkit-flex;
display:flex;
list-style-type:none;
padding:0;
justify-content:flex-end;
}
.left {
margin-right:auto;
}