I'm pretty sure that would go down into the negatives.
Answer:
\frac{13+\left(-3\right)^2+4\left(-3\right)+1-\left(-10-\left(-6\right)\right)}{\frac{\left(4+5\right)}{\left(4^2-3^2\left(4-3\right)-8\right)}+12}=5
Step-by-step explanation:
Let's take any edge length l. The diagonal has length

. In our case it's
x = 2(180 - x) - 12
3x = 348
x = 116
The measure of the angle is 116 degrees.