An equation showing the square footage of a room is a similar equation to the show of linage. Both describe the sum of the two.
A room with walls of 10ft and 20ft would be written as 10' x 20' and spoken; Ten foot "by" Twenty foot.
I am sticking with "crossed with" for the common man, lol! everyone one understands "crossed with". I mean, how many jokes start out, what do you get when you cross a______ with a______?