Dynamic resize of images for mobile platform display

When displayed on a mobile device, the images I’m using for my client’s pages are far too large and make the text around them difficult to read. But I want them to stay this size for desktop display. Is there a way to make them automatically resize to a percentage of their normal width & height when viewed in a mobile browser?

The site dev URL is https://www.voc-research.com/wordpress/

Thanks!