The last part of the Url starts with +E- and shows the input of the calculator. After the dash there is a odd number of characters.
I scraped this from the alt attribute of the images from their website wes.casio.com
For example:
http://wes.casio.com/math/index.php?q=I-251A+U-000B000461EF+M-C10000AA00+S-000410101010100E1010B00051DA+R-0300000000000000010000000000000000000000+E-31A632
which representate 1+2 = 3