/* 背景画像を横幅200px、縦幅130pxで表示したい場合 */
.box {
  width: 100%;
  max-width: 200px;
}

.img-bg {
  width: 100%;
  height: 0;
  padding-top: 65%; /* 横幅の数値÷縦幅の数値×100(%) */
  background-image: url('https://grow-group.jp/wp-content/themes/growgroup-html/dist/assets/images/img-frontpage-service-02.jpg');
  background-size: cover;
  background-repeat: no-repeat;
  background-position: center center;
 
}