Answer:
x = 120
Hope this helps!
Explanation:
The equation to find the total sum of a polygon's angles is ( n - 2 ) * 180, n being the total number of sides. Because this is a 7-sided shape, 7 - 2 is 5, and 5 * 180 is 900. So the total sum of the angles should be 900°. With this known, you can begin to subtract some of the angles from 900, which gives us 360 ( 900 - 130 - 150 - 120 - 140 ). Now the rest of the values ( x + 20, x, and x - 20 ) equal that 360, so you can add them up to get 3x = 360 ( x+x+x, 20 - 20 ). Divide both sides by 3 and x is equal to 120.