How to solve this indicator on the site?

Question

Search Engine Optimization

The site has several pictures inserted and the site is marked with the IMG tag. Using CSS, the images are set to width: 115px; height: 170px;
But the pictures themselves are 171x350px.
In this regard, GTMETRIX gives a warning when testing the site:

We need to solve this. But if I reduce the original image to 115x170 in a graphics editor and paste it on the site, then the quality of the image on the site drops dramatically on the site.
How to solve with this indicator on GTMETRIX and at the same time maintain high image quality on the site?

Answer 1

Just forget it