Answer:
80
Step-by-step explanation:
This is a pentagon (5 sides), n=5
The sum of internal angles equals (n-2)*180 = 540°
We have
A = 90
B = 180-40
C = 180-x
D = 180-60
E = 180-90
Sum all the angles to equal 540°
90 + 180-40 + 180-x + 180-60 + 180-90 = 540
620-x = 540
solve for x
x = 620 - 540 = 80
