Răspuns:
a)
x+58°=180°
x=180°-58°
x=122°
b)
6x+2x=180
8x=180
x=180:8
x=22.5°
c)
3x+6x+20=180
9x=180-20
9x=160
x=160:9
x=17.7°
d)
2x+5x-30=180
7x=180+30
7x=210
x=210:7
x=30°