The answer is 2, because it is asking you, out of the 30 people, who is being counted twice for brown hair and blue eyes. Therefore, you add 17 and 15 to get 32, and because there are only 30 people in the class, you do 32 - 30 = 2 people. Let me know if you're confused or anything :)
290 There's 2 hundreds = 200 Then you have 9 in the tens digit. The only possible answer for the one's digit is 0 since 0 + 9 = 9. So the answer is 290.