<div class="flex">
  <p class="b1">box1</p>
  <p class="b2">box2</p>
  <p class="b3">box3</p>
  <p class="b4">box4</p>
  <p class="b5">box5</p>
  <p class="b6">box6</p>
  <p class="b7">box7</p>
</div>

.flex {
  display: flex;
  width: 400px;
  flex-wrap: nowrap;
}


.b1,.b2,.b3,.b4,.b5,.b6,.b7 {
  border: solid 1px #000;
  height: 50px;
  width: 100px;
}