Operations with sets

Set B - A has twice as few elements as set A - B and four times fewer elements than set A ∩ B. How many times more elements does set A have than set B?

Correct answer:

k =  1.2

Step-by-step explanation:

$$\begin{gathered} B-A=n \\ A-B=2n \\ A\cap B=4n \\ k=A/B \\ k=\frac{A-B\cup A\cap B}{B-A\cup A\cap B} \\ k=\frac{2n+4n}{n+4n} \\ k=\frac{2+4}{1+4}=\frac{6}{5}=1\frac{1}{5}=1.2 \end{gathered}$$

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