Please answer this ( 8th grade math )

Answer:
The correct answer is C
Step-by-step explanation:
Helpful fact- All triangles are 180 degrees
Angle 1 = 31 degrees
Angle 2= 71 degrees
X= Angle 3
Y = Angle 1&2 Sum
So by adding Angles 1 & 2 we get a sum to subtract from 180 and get a difference. That difference will be Angle 3.
Angle 1 + Angle 2 = Y
180 - Y= X
31 + 71 = 102 degrees Y= 102 degrees
180 - 102 = 78 degrees X= 78 degrees
PLS GIVE BRAINLIST IF HELPFUL