The line passing through the points (1, 2, $$-$$1) and (3, $$-$$1, 2) meets the yz-plane at which one of the following points?

Under which one of the following conditions are the lines x = ay + b; z = cy + d and x = ey + f; z = gy + h perpendicular?

What is the distance of the point (2, 3, 4) from the plane 3x $$-$$ 6y + 2z + 11 = 0 ?

Coordinates of the points O, P, Q and R respectively (0, 0, 0), (4, 6, 2m), (2, 0, 2n) and (2, 4, 6) L, M, N and K OR, OP, PQ and QR respectively such that LMNK is a parallelogram whose two adjacent sides LK and LM are each of length $$\sqrt 2 $$ ?