Sum of linear pair of angles = 180°
so
<EFG + <GFH = 180°
2n + 21 + 4n + 15 = 180°
6n + 36 = 180°
6n = 144
n = 24
<EFG = 2(24) + 21 = 69°
<GFH = 4n + 15 = 4(24) + 15 = 111°
