Without figure its not possible. What does this D come from? is it a triangle or quadrilateral or exterior angle? Furnish this information then only it can be solved.
I guess, it is sum of 2 angles. If that is right, 2x + 5x = 91 or 7x =91 or x =13 so 2x = 26. Does that work?
Second is same type I guess!
2x-1 + 5x +2 = 57. So 7x = 56, x = 8. So DBC = 42.