Answer:
B. 10 Degrees.
Step-by-step explanation:
The degrees of the angles on a triangle must have a sum of 180 degrees.
100 + 70 = 170.
180 - 170 = 10.
This is how you know 10 degrees is what the third angle must be.
100 + 70 + 10 = 180.
So, B is your answer.
