a+b+c=180
b=20+a
c=2a
a+(20+a)+2a=180⇒4a=180-20⇒4a=160⇒a=160:4⇒a=40°
a=40° dar b=20+a⇒⇒b=20+40=60°
b=60°
c=2a=2×40=80°
deci a=40°, b=60° si c=80°
2)
perimetrul p=40 cm
AB=a, AC=b si BC=c
b=2c
a=c+4
a+b+c=40
(c+4)+2c+c=40
4c+4=40
4c=36
c=9 cm, BC=9 cm
a=c+4=9+4=13 cm, AB=13 cm
b=2c=18 cm
deci AB=13cm, AC=18 cm si BC=9 cm