**1.In class of 40 students, 38 offer maths, 24 offer English. Each of the students offer at least one of the two subjects. How many students offer both subjects? 2. If A={ 3 ,4 ,5 ,9 and B={1,2,6,9,7}. Find (I) A–B (ii)B n A.**

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1.In the class 40 students, 24 offer English and each of students offer at least one of the two subjects. It means that $40-24=16$ students offer Maths. But we know that 38 students offer Maths. 16 students are not enough 22 to 38 ($38-16=22$ ). But all other student (expect 16 who offer Maths) offer English. It means 22 students offer 2 subjects.

Answer: 22 students offer both subjects.

2. $A= \{ 3,4,5,9 \},B= \{ 1,2,6,9,7 \}$ .

(I) $A-B$ means that from the set A you need to pick up the common elements between A and B or $A-B= \{ x \in A \mid x \notin B \}$ . The common element between A and B is 9. So $A-B = \{ 3,4,5 \}$.

(II) $B \cap A = \{ x \in A \mid x \in B \}$ or the common elements A and B. It's 9. $B \cap A = \{ 9\}$ .

Answer: $A-B = \{ 3,4,5 \}$ , $B \cap A = \{ 9\}$ .

1.In the class 40 students, 24 offer English and each of students offer at least one of the two subjects. It means that $40-24=16$ students offer Maths. But we know that 38 students offer Maths. 16 students are not enough 22 to 38 ($38-16=22$ ). But all other student (expect 16 who offer Maths) offer English. It means 22 students offer 2 subjects.

Answer: 22 students offer both subjects.

2. $A= \{ 3,4,5,9 \},B= \{ 1,2,6,9,7 \}$ .

(I) $A-B$ means that from the set A you need to pick up the common elements between A and B or $A-B= \{ x \in A \mid x \notin B \}$ . The common element between A and B is 9. So $A-B = \{ 3,4,5 \}$.

(II) $B \cap A = \{ x \in A \mid x \in B \}$ or the common elements A and B. It's 9. $B \cap A = \{ 9\}$ .

Answer: $A-B = \{ 3,4,5 \}$ , $B \cap A = \{ 9\}$ .