.boton{
  
  height: 3em;
  width: 3em;
  
}

.visor{

height: 30px;
width: 175px;
font-size: 1em;
 text-align:right; 
}

.historial{

height: 20px;
width: 175px;
font-size: 0.8em;
 text-align:right; 
}

.instrucciones{

  padding-left:15px;
   position: relative; 
  float:left;
  width:80%;
  }
  
.calculadora {
  
  position: relative; 
  float:left;
  align-content:center;
  }