Let P = (2,-3,8) and Q =(4,4,7)
The parametric equation of a line is given by
(x,y,z) = t*(xv,yv,zv) + (x0,y0,z0) where
(xv,yv,zv) is the direction vector PQ which is Q-P => PQ = (4-2, 4-(-3),7-8 ) = (2,7,-1)
And (x0,y0,z0) is any point in the line (for example Q)
So, (x,y,z) = (2t +4 , 7t +4, -t+7)
