The solution to this tough nut was submitted by Ray who does not reveal his school.

By Pythagoras Theorem:
|AB|=3,|BC|=2,|AC|=5,|BD|=5,|AD|=10.

As |AB |2 +|BC |2 =|AC |2 it follows, by the converse of Pythagoras Theorem, that ABC= 90o .

Using the cosine rule: |AD |2 =|AB |2 +|BD |2 -2|AB||BD|cosB. So
cosB= -1 15

and ABD=105 degrees to the nearest degree.

The challenge was to find more than one method so the second method uses geometry and vectors.

cuboid Triangle A* BC is a right angled isosceles triangle and A* B is perpendicular to BC.The line B* B is perpendicular to the plane A* BDC so it is perpendicular to BC. As the two line A* B and B* B are perpendicular to BC the whole plane AB* BA* is perpendicular to BC. Hence AB is perpendicular to BC.
Using vectors :
BA =(-1,-1,-1), BD =(2,0,-1).

So we find the scalar product:
BA . BD =|BA||BD|cosB

which gives
-2+1=35cosB.

Again:
cosB= -1 15

and ABD=105 degrees to the nearest degree.