How do you fix 7.1 Desktop Banners being cropped by 80% on mobile?

/* CSS FOR TABLET AND MOBILE */
@mobile:  ~"only screen and (max-width: 640px)";
@tablet:  ~"only screen and (min-width: 641px) and (max-width: 949px)";

/* CSS FOR TABLET */
@media @tablet {
/* Insert Code for Tablet Below This Line*/

/* Insert Code for Tablet Above This Line */
}

/* CSS FOR MOBILE */
@media @mobile {
/* Insert Code for Mobile Below This Line*/

/* Insert Code for Mobile Above This Line */
}

Resizing Image Blocks Site-Wide

.sqs-block-image {
  width: 80%;
  margin: 0 auto;
}