Just give them a width and float: left;, here’s an example:
Left Stuff
Middle Stuff
Right Stuff
The modern way is to use the CSS flexbox, see support tables.
.container {
display: flex;
}
.container > div {
flex: 1; /*grow*/
}
Left div
Middle div
Right div
You can also use CSS grid, see support tables.
.container {
display: grid;
grid-template-columns: 1fr 1fr 1fr; /* fraction*/
}
Left div
Middle div
Right div