Answer:
B.
Step-by-step explanation:
A- 12 + 5 = 17 (Cannot be the same)
B- 10 + 15 = 25 (More than the 3rd side) ✅
C- 9 + 11 = 20 (Cannot be less than the 3rd side)
D- 7 + 6 = 13 (Cannot be less than the 3rd side)

this is because when you add

and

you get

which you'd then divide like this

If you wanted to simplify that it would be
Answer:
top angle = 59
n= 12
submitted with n and you will get each angle
- - - - - - - - -
X = 32°
C= 67°
If you have the two other angle measures:
You can add the angles together and subtract them from 180.
Example:
Angle 1: 90
Angle 2: 45
Angle 3: ?
90 + 45 = 135
180 - 135 = 45
Angle 3 is 45 degrees.
This is because all three angles of a triangle need to be equal to 180 when added up.
It would be:
(8 x 3 + 6) divided by 15
because of PEMDAS.