Hi Richard,
If you remove .page-id-56 from your code it will affect all pages.
If you want to target specific pages and not all pages you need to find out each page page-id
And change the code for *for example
.page-id-56 .x-column.x-sm.x-1-2 .x-img img,
.page-id-56 .x-column.x-sm.x-1-2 .x-img ,
.page-id-27 .x-column.x-sm.x-1-2 .x-img img,
.page-id-27 .x-column.x-sm.x-1-2 .x-img ,
.page-id-33 .x-column.x-sm.x-1-2 .x-img img,
.page-id-33 .x-column.x-sm.x-1-2 .x-img {
width: 100%
}
3 Easy Ways to Find the Page ID in WordPress
Hope that helps
joao