Answer: Part 1, 360
Part 2, (x + 300 = 360)
Part 3, x = 60°
Step-by-step explanation: First things first, the figure given in the question is a quadrilateral (four sided figure). The sum of the interior angles of a quadrilateral equals 360°.
So, if three angles have been given and one angle is yet unknown, to calculate the unknown angle we simply write out the expression
Sum of interior angles = 360
x + 91 + 120 + 89 = 360
x + 300 = 360
Subtract 300 from both sides of the equation
x = 60.
Therefore, the fourth angle x measures 60°
