Find an orthogonal projection of (6, 0, 0)

(1) along the vector (1, 2, 1)
(2) On the plane determined by (1, 2, 1) and (1, −1, 1)
(3) On the subspace spanned by (1, 2, 1), (1, −1, 1) and (3, 0, −3)