Okay so to find what all of the angles are supposed to add up to, you use the formula 180(n-2).
180 is what a straight line is.
So for a pentagon which has five sides, you subtract two (the number of sides are n in the equation).
180(5-2)
180(3) = 540.
The sides should add up to 540 degrees.
If four of the sides already equal 440, subtract that from 540.
540-440=100.
The fifth angle is 100 degrees.
I hope that helps!
