Find x so that the triangle with vertices A= (1, 9, -8) B= (-1, x , -17) and C = (3, 1, -11) has a right angle at A

Answer 1

Wonder why the bot, or the AI, or whatever it calls itself, is not capable of
answering this question.

vector AB = (-2, x-9, -9)
vector AC = (2, -8, -3)
to have a right-angle at A , AB dot AC =0
-4 - 8x + 72 + 27 = 0
-8x = -95
x = 95/8