( a + b + c ) / 3 = 14 ⇒ a + b + c = 3 · 14 = 42
a = 30% ·b = 30·b / 100 = 3·b /10
b / 5 = c / 4 = k b = 5k ; c = 4k
a = 3· 5k /10 = 3k / 2
3k / 2 + 5k + 4k = 42
3k + 10k + 8k = 2·42
21 · k = 2 · 42 impartim cu 21
k = 2 · 2 = 4
a = 3 · 4 / 2 = 6 ; b = 5·4 =20 c = 4 · 4 =16