If D is the center of the circle, ∠ADB = 70°, as that is where the arc gets its measure.
If D is on the circle and not on the arc, ∠ADB = 35°, half the measure of the arc's central angle.
If D is on arc AB, then ∠ADB = 145°, half the measure of the corresponding central angle.
If D is inside or outside the circle (and not one of the above), we need to know more about the measures of arcs intercepted by lines AD and BD.
