Find measure of ∠ CBD in the following figure: 
In the following diagram:
∠ ABC = 40° (given)
∠ CBD is exterior angle
And ∠ABC is adjacent interior angle to exterior angle ∠ ABC
Therefore, ∠ ABC & ∠ CBD from a Linear Pair; so:
∠ ABC + ∠ = 180°
Put the Value of ∠ ABC from above and we get:
40° + ∠ CBD = 180°
Subtract 40°
∠ CBD = 140°
Hence, measure of ∠ CBD is 140° 
Related Question Examples
What can you say about the sum of an exterior angle of a triangle and its adjacent angle ? 
Find measure of ∠ CBD in the following figure: 
Find the measure of adjacent interior angle of a triangle, whose exterior angles is 80° 
