The measure of angle A is 55°.
Solution:
Let us take B be the adjacent angle of 145°.
Sum of the adjacent angles in a straight line = 180°
⇒ m∠B + 145° = 180°
Subtract 145° from both sides.
⇒ m∠B + 145° - 145° = 180° - 145°
⇒ m∠B = 35°
The adjacent angle of 145° is 35°.
In the image, angle B and angle A equal to 90°.
⇒ m∠B + m∠A = 90°
⇒ 35° + m∠A = 90°
Subtract 35° from both sides.
⇒ m∠A = 55°
The measure of angle A is 55°.
