The problem set 18 {1, 2,3,4,5} is equivalent to the set {x | x < = 5, and x is a natural number}.

correct

The question 17 A∈{A} is a true proposition.

correct

Question 18 if a, b and c are sets, (A-B)-C=A-(B-C)

mistake

Question 7 {x|x/5=k, k= integer} represents a group of integers divisible by 5.

correct

Question 8: "Blue and yellow can match green" is a proposition.

correct

Question 9 "Wang Daming and Wang Xiaoming are brothers" is a proposition.

correct

The question 10 "If 2+2=5, then 3+3≠6" is a true proposition.

correct

The power set of the problem 12 {empty set} is {empty set, {empty set}}

correct