a + b + c = 713
a = 2×b
c = 2×a + 13 => c = 4×b+13
inlocuim in prima relatie in functie de b
2×b + b + 4×b + 13 = 713
7×b = 713 - 13
7×b = 700
b = 700 : 7
b = 100
a = 2×100 = 200
c = 4×100+13 = 400 + 13 = 413
verificare:
200 + 100 + 413 = 713
a = 200
b = 100
c = 413