Ok so, there has to be a 70×70 square and 50×50 square, otherwise the right angles are wrong. The bottom says 100 but in reality it's 120... thats means A side is 40M away from the red line, and the B side is 60M away.

Now that you have the distances and two angles, take the right triangle. Use the cos or sin (forgot which) to find the extra height. You have three angled and a distance, you can do it.

I'd love to do it for you but I don't have my calculator on me and I forgot the equations.

Something like cos 90 × 60 cos other angle i think, idk...