Body background to 1 page

Is there an easy way to add an background image to the body of a certain page. At the moment i can do that option in customiser but this will then apply to all the pages. The ID of my page is post=48528 i think. I tried

.page-id-48528 {
    background: #FFFFFF;
    opacity: 0.9;
}

.page-id-48528 .body { 
background: url(‘www.zilvertron.com/wordpress/media/zilvertron/DeSmaragd15.jpg’); }

but that did not work. Any ideas how i can fix this?
Also as you can see i want to make the content of the page transparent.

Thanks for your time,

Sjoerd