2x + 3y = 31 ...(i) y – z = 4 ...(ii) x + 2z = 11 ...(iii) Multiplying equation (ii) by 2 and adding with (iii) we get x + 2y = 19 ...(iv) Multiplying equation (iv) by 2 and subtracting (i) from it, we get, y = 7, From equation (ii) z = y – 4 = 7 – 4 = 3 From equation (iii) x + 2 × 3 = 11 ⇒ x = 5 Now, x + y + z = 5 + 3 + 7 = 15