#marco {
    border: 1px solid black;
    position: absolute;
    height: 400px;
    width: 350px;
    background-color: turquoise;
    top: 50px;
    left: 50px;       
}



#pantalla {
    position: absolute;
    border: 1px solid black;
    height: 60px;
    width: 245px;
    background: white; 
    top: 50px;
    left: 50px;
    
}    
    
    
#botones{
    width: 245px;
    position: absolute;
    top: 150px;
    left: 50px;
}


#botones-numeros{
    position: absolute;
    background-color: grey;
    width: 150px
}


#botones-operaciones{                    
    background-color:grey;
    position:absolute;
    left:150px;
}


button {
    border: none;
    color: black;
    padding: 10px 15px;   
    text-align: center;
    display: inline-block;
    font-size: 16px;
    margin: 4px 2px;
    cursor: pointer;
}




h3{
    margin: 4px 4px;
    text-align: right;
    
    
}

h5{
    text-align: center;

}