Answer:
45°
Explanation:
All of the angles in a triangle must add up to 180°.
This is a right triangle because of the presence of a right angle (denoted by the little box in the bottom left-hand corner). All right angles equal 90°.
You were given the value of another angle, 45°.
Therefore, the value of the final angle must be,
x + 90° + 45° = 180°
x + 135° = 180°
x = 45°