Answer:
50°
Explanation:
Note that all the three angles inside a triangle always add up to 180°.
Here, the three angles we have are ?, 40°, and the right angle at the bottom. Right angles are equal to 90°
So this is what adding all the angles in this triangle looks like: ?+40°+90°, and this is going to equal 180°, so we have:
?+40°+90°=180°
?+130°=180°
?=180°-130°=50°