Answer:
87 degrees
Explanation:
The triangle with the angles 79 and 15, we can find the last value because all angles in a triangle add up to 180. So, 180-79-15= 86 degrees for the angle of the triangle.
Because the 86 degree angle is complimentary, or when added up to the adjacent angle, is 90 degrees (we see that little box sign), that means that 90-86=4 degrees for the upper triangle in the angle that isn't the question mark. Now that we know 2 values for the top triangle, we can solve for the third value by subtracting those two from 180.
180-89-4=87 degrees. Hope this helps!