.container{
    text-align: center;
}
.question-number{
    min-height: 30px;
    text-align: left;
    font-size: 20px;
}
.question{
    height: 300px;
}
.question td{
    border: 3px solid;
    text-align: center;
    height: 90px;
    width: 90px;
    font-size: 40px;
}
table.center{
    margin-left: auto;
    margin-right: auto;
}
.next-prev{
    text-align: center;
    margin-top: 20px;
}
a {
  text-decoration: none;
  display: inline-block;
  padding: 8px 16px;
}
a:hover {
  background-color: #ddd;
  color: black;
  text-decoration: none;
}
.previous {
  background-color: #f1f1f1;
  color: black;
}
.next {
  background-color: #4CAF50;
  color: white;
}
.round {
  border-radius: 50%;
}
.solution{
    float: left;
}
.hid{
    color: red;
    font-weight: bolder;
}
#numb{
    border: 1px solid #000;
}

@media only screen and (max-width: 900px) {
  body {
    background-color: lightblue;
  }
    img{
        width: 500px;
        height: 200px;
    }
}