I don't understand to which angel the expression angel BDO in a triangle refers? Is it the angelt at B, D or O? It cannot be to the triangle itself because then it would always be 180 degree or not?
Sorry for that stupid question.
In general the GMAT question will contain the diagram, and the angle in that case would be formed by the line segments BD & DO.
My posts: Solving Inequalities, Solving Simultaneous equations, Divisibility Rules
My story: 640 What a blunder!