How do you solve problems like this?

Acommunity group sells 2,000 tickets for its raffle. the grand prize is a car. neil and 9 of his friends buy 10 tickets each. when the winning ticket number is announced, it is found to belong to neil's group. given this information, what is the probability that the ticket belongs to neil? a.1/5 b.1/10 c.1/200 d.1/4

Factor k2 - 17k + 16. a.(k - 2)(k - 8) b.(k - 1)(k + 16) c.(k - 1)(k - 16)

Some boys and girls were asked if they had a pet. one third of the group were boys. there were 20 boys. 20% of the girls had a pet. boys with a pet : girls with a pet = 1 : 5 i need to know how many girls there are.