[SOLVED] Venn diagram shows the universal set U and the sets A and B.

[karush]

View attachment 1175

(b) $A'=100-30=70$ and since $n(A\cup B) = 65$ and $A+B=80$
then $n(A\cap B)= 15$ so $n(B\cap A')=70+15=85$

(c) $\displaystyle\frac{n(B\cap A')}{n(U)}=\frac{85}{100}=\frac{17}{20}$

or ????

 

[Plato]

This is \(\displaystyle B\cap A'\)

 

[karush]

so I have $B\cup A'$

(c) $\displaystyle\frac{n(B\cup A')}{n(U)}=\frac{35}{100}=\frac{7}{20}$

 

[MarkFL]

so I have $B\cup A'$

(c) $\displaystyle\frac{n(B\cup A')}{n(U)}=\frac{35}{100}=\frac{7}{20}$

That is correct.