HEF is a Line.
∠HED=90°------[Given]
So, ∠DEF=180° -90°------By Linear Pair Axiom
→6x+4x=90°
→10 x=90°
Dividing both side by 10
→x=9°
→∠DEG=6×9°=54°
→∠GEF=4×9°=36°
