Customize table cells

Trying to remove the white space between the 3 images in the table on this page:

http://richsride.org/frontrangefreedomtour/

Pretty sure it’s due to the margin or padding at the top/bottom of cells which won’t allow images to expand. I’m trying to use css but just don’t know the syntax. “FRFT Top” is the id of the table, I placed the code in the css of a child theme and got nothing.

#FRFT Top td {
padding: -6px -10px -6px 0px;
margin: -9.09 px;
}

Can someone help with proper syntax? I can play with the numbers.

Thanks.