create a path that encloses the part of the jpg that you do want shown, select that path and the jpg, and hit ctrl+7 (or 'object' > 'clipping mask' > 'make'. Then the only visible part of the jpg is that which is within the clipping mask (path that you created). You can hit ctrl+alt+7 to release the clipping mask, or use your node edit tool to adjust as necessary.
-E
(DISCLAIMER: Self-taught AI user; unorthodox methods w/good results)
'There is no LEASH LAW for the IMAGINATION!'
myspace.com/erixworx