Thinking 21. Given x = (2,5), ỷ = (-5, 12) find the scalar projection of x on ỷ. 22. If (-1, 3, 5) x (0, a, 1) = (-2, 1, -1), determine a.▸ 23. Given = [1, 7, 9] and, v = [-2, 5, -3] and w = [4, -6, 8]. a) Find the angle between v and w. b) Are the vectors u and v and w coplanar? Show your answer algebraically.