#cuerpo {width: 99%;
        background: #33FFFF;
        font-size: 23px;
}
article {color: #000000;
    display: inline-block;
    margin: 0px 300px;
    font-size: 28px;
}
#Explicación { text-align: center;
            width: 87%;
            height: 35px;
            display: inline-block;
            border: 2px solid #9933FF;
            color: #000000;
 }
#Actividad { text-align: left;
            width: 87%;
            height: 670px;
            display: block;
            border: 2px solid #9933FF;
 }
 #columna {width: 12%;
    height: 503px;
    text-align: center;
    display: inline-block;
    float: right;
}
#Comprobar {
  border-radius: 10px;
    padding-bottom: initial;
    color: #FFFFFF;
    background-color: blue;
    width: 120px;
    height: 50px;
    margin: 30px auto;
    font-size: 20px;  
}#Comprobar:hover{ 
        cursor:pointer
}
#Solución {
  border-radius: 10px;
    padding-bottom: initial;
    color: #FFFFFF;
    background-color: red;
    width: 120px;
    height: 50px;
    margin: 30px auto;
    font-size: 20px;  
}#Siguiente {
  border-radius: 10px;
    padding-bottom: initial;
    color: #FFFFFF;
    background-color: red;
    width: 120px;
    height: 50px;
    margin: 30px auto;
    font-size: 20px;  
}
#Principal {
  border-radius: 10px;
    padding-bottom: initial;
    color: #FFFFFF;
    background-color: red;
    width: 120px;
    height: 50px;
    margin: 30px auto;
    font-size: 20px;  
}
#cabecera {background: #FFCCFF;
        padding: 10px;
        width: 97%;
        height: 50px;
        border: 3px solid #9933FF;
}
img {width: 50px;
    display: inline-block;
}#ok{
     width: 75px;   
}
#tito{
        width: 300px;
        height: 400px;
}
#tabla {margin: 10px 20px;
        background-color: lightpink;
        border: 2px solid #000000;
        width: 760px;
        display: inline-block;
}.filabor{
        height: 50px;
        display: inline-block;
}.enunciado{
        margin: 10px auto;
        text-align: left;
        font-size: 30px;
}.resultado{
        margin: 15px 300px;
        text-align: left;
        font-size: 40px;
}.cel{
        width: 40px;
        border: 1px solid #000000;
        font-size: 37px;
        text-align: center;
        color: blue;
}.celd{
        width: 280px;
        border: 1px solid #000000;
        font-size: 37px;
        text-align: center;
        color: blue;
}.celt{
        width: 455px;
        border: 1px solid #000000;
        font-size: 37px;
        text-align: center;
        color: blue;
}
.dob{
        width: 65px;
        border: 1px solid #000000;
        font-size: 37px;
        text-align: center;
        color: blue;
}.cantidad{
        color: red;
}.resp{
        width: 70px;
        height: 45px;
        background-color: white;
        color: red;
        text-align: center;
        font-size: 40px;
}
.cajasim{
        width: 30px;
        height: 30px;
        background-color: pink;
        text-align: center;
        font-size: 20px;
        color: blue;
}.cajamul{
        width: 250px;
        height: 30px;
        background-color: pink;
        text-align: center;
        font-size: 20px;
        color: blue;
}#mensajeok{
        font-size: 70px;
        color: #9933FF;
        background-color: white;
        margin: 10px 200px;
        display: none;
}#mensajeno{
        font-size: 70px;
        color: #9933FF;
        background-color:white;
        margin: 10px 150px;
        display: none;
}input[type=button], input[type=text]{
        width: 100%;
        height: 100%;
        font-size: 30px;
        background: orange;
        }
        #calc, form{
        width: 250px;
        height: 200px;
        margin:70px 20px;
        display: inline-block;
        }

<!--Para que no aparezcan las flechitas en la caja --> 
input[type=number]::-webkit-inner-spin-button, 
input[type=number]::-webkit-outer-spin-button { 
  -webkit-appearance: none; 
  margin: 0; 
}
//Firefox:
input[type="number"] {
-moz-appearance: textfield;
}
input[type="number"]:hover,
input[type="number"]:focus {
-moz-appearance: number-input;
}
input[type=number] {
    -moz-appearance:textfield;
}