Answer:
We know that the sum of the the interior angles of a quadrilateral is 360°.
In the figure, angle H = angle F
angle H+ angle F+ angle E+ angle G =360°
[tex]x + x + 87 + 31 = 360 \\ 2x + 118 = 360 \\ 2x = 242 \\ x = \frac{242}{2} \\ \boxed{x = 121}[/tex]
Therefore, Angle F = 121°.
