a and b are two sets such that

n(a-b)=20+x

n(b-a)=3x

n(a∩b) =x+1 if n(a)= n(b)

the value of x

*n(a-b)=20+x*

*n(b-a)=3x*

*n(a**∩**b) =x+1*

We know that

*n(a-b) = n(a)-n(a**∩**b)*

*∴n(a) = n(a-b) + n(a**∩**b)*

* = (20+x) + (x + 1)*

* = 2x + 21*

Similarly,* n(b) = n(b-a) + n(a**∩**b)*

* =3x + (x+1)*

* =4x + 1*

According to the question,

*n(a) = n(b)*

*∴2x + 21 = 4x +1*

*⇒2x = 20*

*∴**x = 10*

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