SOURCE

<div id="phone">
   <div id="box">
     <div id="item1">
       <h1>itm1</h1>
     </div>
     <div id="item2">
       <h4>itm2</h4>
     </div>
     <div id="item3">
       <h1>itm3</h1>
     </div>
     </div>
  </div>

#phone {
border:2px solid red
width:375px  
height:200px
}
#box {
  display:flex;
  flex-direction:row;
  justify-content:center;
  align-items: baseline;
  height:200px;
}
#item1{
  background-color:red;
}
#item2{
  background-color:blue;
}
#item3{
  background-color:pink;
}