table,th,td{
    border: 1px solid black;
    border-collapse: collapse;
}

th,td{
    text-align: center;
}
table{
    width: 100%;
    background-color: rgba(107, 184, 144, 0.923);
}
body {

    background-image: url("../image/math.jpg") ;
    background-repeat: repeat-y;
    background-attachment: fixed;
    background-size: cover;
}