设这个三位数的是abc, 其中a、b、c分别是是百位、十位和个位上的数字 则这个三位数是 100a + 10b + c, 由已知条件有 a + b + c = 11 (100c + 10b + a) - (100a + 10b + c) = 693 (100a + 10c + b) - (100a + 10b + c) = 54 整理得 a + b + c = 11 c - a = 7 c - b = 6 三式相加得3c = 11 + 7 + 6 = 24 c = 8 a = 1 b = 2 所以此三位数是128.