Which three nations do the tigris and euphrates rivers flow through

The rivers passes the nations Turkey, Syria, and Iraq.

5×^2+20-15 or -(5x^2-20+15)

It is useful for historians to write narratives so that history can be passed on from their point of view.  think about a story being told in third person, then think about it again being told in first person, by someone who actually experienced the event.