How can I know the real value of this?

I found it in a estate sale! More pictures as reference

 

The only way to truly find value is to sell it in a marketplace with good exposure. That said, there are ways to evauate and approximate value. You have not provided us with enough information to even attempt to do this.

 

Welcome, Laura

The first step is a proper identification. We cannot read the newspaper clipping that you have posted. Does it name the artist? Can you tell us if your picture appears to be a painting, or a print? If you cannot tell, we may be able to if you can post detailed closeup photos. When you include photos in your post, please select the option of Full Size rather than Thumbnail, which makes it easier for us to see. What is the size of your picture? Do you know any history about it?

 

The original oil painting, Young Woman Drawing, is in the Metropolitan Museum of Art in New York City. It is also known as the Portrait of Charlotte du Val d’Ognes.

Once attributed to Jacques-Louis David, then to Constance-Marie Charpentier, it is now believed to be by Marie-Denis Villers. It is dated to 1801.

Maybe a print?

https://en.wikipedia.org/wiki/Marie-Denise_Villers

Edit, added a link and other title of the painting.

 

A google search turns up this information -

https://www.google.com/search?q=mar...CDczNzJqMGo0qAIAsAIA&sourceid=chrome&ie=UTF-8

 

This looks like one of the prints they made for "pretty" back in the 50s and 60s. There's no chance this is a real painting.