How many integers between 100 and 500 have at least two 3s as digits?
13 = 133, 233, 330, 331, 332, 333, 334, 335, 336, 337, 338, 339, 433.
there is way more
303,323,343,353,363,373,383,393
so the answer is 18+3=21
+335 
