In the figure, DEF is a straight line. $\angle DEH = 150^\circ$ and $\angle GEF = 110^\circ$. Find $\angle GEH$. Answer: ___ $^\circ$

1. Find $\angle HEF$ using angles on a straight line

Since $DEF$ is a straight line, the sum of angles on it is $180^\circ$.
$\angle HEF = 180^\circ - \angle DEH$
$\angle HEF = 180^\circ - 150^\circ = 30^\circ$

2. Find $\angle GEH$ by subtracting $\angle HEF$ from $\angle GEF$

$\angle GEH = \angle GEF - \angle HEF$
$\angle GEH = 110^\circ - 30^\circ = 80^\circ$