Spotter is a program that lets students check 
their answers to math and science questions. 
It handles symbolic as well as numerical answers. 
The software is free and open source.

I got the idea for Spotter from LON-CAPA, which 
is also free and open-source. The programs are alike 
in some ways and different in others. There is another 
program called WeBWorK that also does similar things; 
it doesnt cost money, but Im not sure if its...