.ppt-list {
    width: 100%;
}

    .ppt-list .item {
        position: relative;
        width: 48%;
        padding: 0;
    }

        .ppt-list .item:nth-child(2n) {
            margin-right: 0;
        }

        .ppt-list .item .img-box {
            height: auto;
            width: 100%;
            overflow: auto;
        }