consider the line in 2D ax+by+c=0. Then the vector (-b,a) is always // to this line. you must know this....
to find the parametric equation of a line you need the vector // to the line and one point of the line.
in your case get one point of the line...example put x = 1 and find the y = -5
therefore the parametric equations of the line 2x+y+3=0 are x= 1-t and y = -5 +2t.
you may work similarly for the second question