It is possible to to simple mathematics directly on scantables from the command line using the +, -, *, / operators as well as their cousins +=, -= *=, /=. This works between two scantables or a scantable and a float. (Note that it does not work for integers).
ASAP> sum = scan1+scan2 ASAP> scan2 = scan1+2.0 ASAP> scan *= 1.05