.......the answer is 7.26
Imagine

at the top of the triangle and

at the bottom. (or used the attached picture for reference)


One thing to note, however, is that the side opposite

is the same side as the one adjacent to

! Thus

.
Substitute these values for

and

and solve.
Answer:
114.8 degrees
Step-by-step explanation:
supplementary angles basically means angles equal to 180 degrees
The original area of a face would be a^2. Now that you added b to the edge, the new area of each face would be (a+b)^2. To find how much the are increased, subtract a^2 from (a+b)^2.
So the answer is b(2a+b)