css - 图片的宽度发生变化而高度却没有相应变？

图片高度没有出现相应的变化

HTML

  
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CSS

.snippet__thumbnail > img {
    width: 100;
}

.snippet {
    display: flex;
    flex-wrap: wrap;
}

.snippet__thumbnail {
    order: 1;
    width: 30%;
}

.snippet__title {
    order: 0;
    width: 100%;
    margin: 0 0 0.5em;
}

.snippet__description {
    order: 2;
    max-width: 70%;
    margin: 0;
    padding: 0 0 0 1em;
    overflow: hidden;
    display: -webkit-box;
    -webkit-box-orient: vertical;
    text-overflow: ellipsis;
}

疑惑

为什么图片的高度不会随着宽度一起变化？
理论效果应该如此：