x / 3 = y / 7 = z / 11 = k ⇒ x = 3 k ; y = 7 k; z = 11 k
x + 2 y + 3 z = 200
3 k + 2 × 7 k + 3 × 11 k = 200
3 k + 14 k + 33 k = 200
50 k = 200 ⇒ k = 200 : 50 ⇒ k = 4
x = 3 × 4 = 12
y = 7 × 4 = 28
z = 11 × 4 = 44
Verific: 12 + 2 × 28 + 3 × 44 = 12 + 56 + 132 = 200