List the number have exactly 1 number 8 from 100 to 400 : 108, 118, 128, 138, 148, 158, 168, 178, 180, 181, 182, 183, 184, 185, 186, 187, 189, 198, 208, 218, 228, 238, 248, 258, 268, 278, 280, 281, 282, 283, 284, 285, 286, 287, 289, 298, 308, 318, 328, 338, 348, 358, 368, 378, 380, 381, 382, 383, 384, 385, 386, 387, 389, 398 ( 188, 288, 388 is elminate because have 2 8s)

So there are 54 number have exactly 1 number 8 from 100 to 400