Hard Math

I <a href="http://www.flickr.com/photos/maisonbisson/201844037/">found this photo</a> at <a href="http://www.joe-ks.com/archives_sep2005/MennoniteMath.htm" title="Mennonite Longhand Math">joe-ks.com</a>. The title there is “Mennonite longhand math,” but can anybody identify the source or context? Can anybody work out the equation on the board? I've convinced my friend <a href="http://www.flickr.com/photos/maisonbisson/53151695/">Will</a>, who teaches math and physics, to pose for a shot like this, but that means we'll have find and fill a huge chalkboard...and he'll have to grow his beard back. » about 100 words