Since the polygon has seven angles we deduce it is a heptagon. In that case the sum of the interior angles must be equal to 900°. We can formulate the following equation accordingly.
120°+(4*x-3)°+ (x+14)°+ 45°+ 135°+ (x-31)°+ (x*6+20)° = 900°
120°- 3° +14° + 45° + 135° - 31° + 20 + 4x + x + x + 6x = 900° (Organizing)
300 ° + 12x = 900° (Operating like terms)
12x= 900° - 300° (Transposing 300° to the other side of the equation)
12x= 600° (Subtracting 300° from 900°)
12/12x= 600° / 12 (Dividing by 12 on both sides of the equation)
x= 50°
Answer is: x= 50°
