"Sage is a free mathematics software system licensed under the GPL. It combines the power of many existing open-source packages into a common Python-based interface." The installation on my laptop with Ubuntu was very simple. I went to console/terminal and issued:
## Unpack and remove the tarball
tar xzvf sage-*.tar.gz
rm -f sage-*.tar.gz
## Move to /usr/local
sudo mv sage-* /usr/local/.
## Make link
sudo ln -s /usr/local/sage-*/sage /usr/local/bin/sage
The whole "distribution" is quite big, the tarball has 366 Mb, while the unpacked directory has 1.2 Gb.