A die is thrown. $A = \{1, 2, 3, 4\}$ and $B = \{3, 4, 5\}$. How many outcomes are in 'A but not B'?

Explanation

1. 01

   'A but not B' is $A \cap B'$: the outcomes of $A$ that are not in $B$.

2. 02

   Removing 3 and 4 from $A$ leaves $\{1, 2\}$: 2 outcomes.