(4) Let the two – digit numberbe 10x + y where x > y. According to the question, x + y = 12 ......(i) x – y = 6 .......(ii) On adding equations (i) and(ii), 2x = 18 ⇒ x = 9 From equation (i), 9 + y = 12 ⇒ y = 12 – 9 = 3 ∴ Number = 10x + y = 9 × 10 + 3 = 93 ∴ When x < y, Number = 39