Answer:
51°
Explanation:
Remember, all 3 angles must add up to 180°
We can tell that this triangle is a right triangle, or a triangle that has a 90° angle. We also have another angle given, which is 39°. Currently we have two angles given.
Since all 3 angles have to add up to 180°,
90 + 39 + x = 180°
129 + x = 180°
180 - 129 = x
x = 51°
The missing angle is 51°
To see if your calculation is correct, you could add all 3 angles, and it should give you 180 as a sum.
90 + 39 + 51 = 180
Correct!