(10H + A) - (10A + H) = 18 10H + A - 10A - H = 18 9H - 9A = 18 Divide through by 9 H - A = 2 -------------------------------------------- Note that there is no way to find H and A. In fact there are seven possibilities: HA = 31 and AH = 13 or HA = 42 and AH = 24 or HA = 53 and AH = 35 or HA = 64 and AH = 46 or HA = 75 and AH = 57 or HA = 86 and AH = 68 or HA = 97 and AH = 79 But in each of these 7 cases, H - A = 2 Edwin