Use this formula to get the total angle measurement of the figure:
T=180(n-2)
Since there are 7 sides, the total measurement must be:
180(7-2)
180(5)
900 degrees
Set up an equation and solve for x:
123+121+127+128+139+125+x=900
763+x=900
x=137
So the missing angle is 137 degrees.
Hope this helped!
