Answer: The required measure of angle JGH is 150°.
Step-by-step explanation: We are given to find the measure of angle JGH.
From the figure we note that
FH is a straight line and JG is a ray on line FH, thereby making angle FGH to be a straight angle.
So, angles JGF and JGH makes a linear pair.
Also, m∠JGF = 30°.
Therefore, we get

Thus, the required measure of angle JGH is 150°.