1. The problem states that three angles on a straight line add up to form a straight angle. 2. A straight angle measures exactly 180 degrees. 3. The three angles given are 65°, $b^\circ$, and 20°. 4. The sum of these angles must equal 180°: $$65 + b + 20 = 180$$ 5. Combine the known angles: $$85 + b = 180$$ 6. To isolate $b$, subtract 85 from both sides: $$\cancel{85} + b = 180 - \cancel{85}$$ $$b = 95$$ 7. Therefore, the value of $b$ is 95 degrees.