.single-image-desktop img{
    width:100%;
  }
  .single-image-mobile img{
    width:100%;
  }

 @media screen and (min-width:749px){
    .single-image-mobile{
      display:none;
    }
  }

  @media screen and (max-width:750px){
    .single-image-desktop{
      display:none;
    }
  }