a) 3x + x =180°
4x=180°/:4
x= 45°
b) x+x+100=180°
2x + 100°=180°/-100°
2x=80°/:2
x=40°
c) 2x+x+102°=180°/-102°
3x=78°/:3
x= 26°
d) x+3x+20°=180°/-20°
4x=160°/:4
x=40°
e) 2x+3x+72°+x=180°/-72°
6x=108°/:6
x=18°
f) 60°+2x+40°+2x+x=180°/-60°+40°
5x=80°/:5
x=16°
