Question

a+b=40          b+c=30           c+a=30

Answer 1

adunam cele 3 ecuatii
2×a+2×b+2×c = 40+30+30
2×(a+b+c) = 100
a+b+c = 100 : 2 = 50
a+b =40
c = 50-40 = 10

b+c = 30
a = 50-30 = 20

c+a = 30
b = 50-30 = 20

Verificare:
20+20+10 = 50

a = 20
b = 20
c = 10