I don't know how to do the column vector in LaTeX; so I'll use the horizontal equivalent.
Q7.
[x, y, z] = [2, 1, 3] + \lambda [1, 1, 2] \\ \\ = [2, 1, 3] + [1, 1, 2] + \frac {\lambda - 1}{2} [2, 2, 4] = [3, 2, 5] + \mu [2, 2, 4]
Therefore the same line.
For vector eqn of a line: you have one...