Okay, to solve this question, we'll need to find the relationship between angle A and
angles B and C.
So to begin, please notice that we have two angles on the same line here.
As such, these two angles must add to be 180. So if one angle is B, the other angle must
be 180 minus B.
The same concept applies over here. We have two angles that must add to be 180. One angle
is C, so the other angle must be 180 minus C.
Now let's focus on this triangle here. We have all three angles in this triangle, and
we know the sum of those three angles must be 180. So we can write the following equation:
From here, we can simplify the left hand side, and now let's subtract 180 from both sides.
Finally, let's add B and add C to both sides of our equation to get a + 180 = b + c.
At this point, we can go up to column A and replace 180 + a with b + c.
At this point, we can see that column A equals column B, so our answer must be C.
