Need help finding the coordinate for perpendicular line in 3d space

[Johnnyhuman]

Hello. My problem relates to perpendicular lines in 3d space. I have 3 lines L, M and N connecting the points Pa, Pb, Pc and Px.
Pa, Pb, and Pc are known. I need help finding the coordinates for Px. Line L is perpendicular to M and N.

 

[stapel]

Hello. My problem relates to perpendicular lines in 3d space. I have 3 lines L, M and N connecting the points Pa, Pb, Pc and Px.

Pa, Pb, and Pc are known. I need help finding the coordinates for Px. Line L is perpendicular to M and N.

What methods, rules, formulas, etc, did they give you in class? What have you tried? How far have you gotten? Where are you stuck?

Please be complete. Thank you!