16. a+b+c = 72 b+c = 3a c-b =b/2 + 4 |x2 2c-2b = b + 8
a + 3a = 72 a = 18
b+c = 54 |x3
2c - 3b = 8
----------------------
5c = 162+8 5c = 170 c = 34 b = 20
17. a+b+c+d = 48 ( cu 42 nu se obtin numere naturale)
a = 2x b = 2x +2 c = 2x+4 d = 6x+6
12x +12 = 48 12x = 36 x = 3
a = 6 ; b = 8 ; c = 10 ; d = 24
