1. **State the problem:** We are given sets and asked to find the set difference $B - A$ where $U = \{x \mid x \text{ is a natural number less than } 20\}$, $A = \{x \mid x \text{ is a multiple of } 5\}$, $B = \{x \mid x \text{ is a multiple of } 3\}$. 2. **Find the elements of each set:** - $U = \{1, 2, 3, \ldots, 19\}$ - $A = \{5, 10, 15\}$ (multiples of 5 less than 20) - $B = \{3, 6, 9, 12, 15, 18\}$ (multiples of 3 less than 20) 3. **Calculate $B - A$:** This means elements in $B$ that are not in $A$. $B - A = \{3, 6, 9, 12, 15, 18\} - \{5, 10, 15\} = \{3, 6, 9, 12, 18\}$ 4. **Binary subtraction $110_2 - 10_2$:** - Convert to decimal: $110_2 = 6$, $10_2 = 2$ - Subtract: $6 - 2 = 4$ - Convert back to binary: $4 = 100_2$ 5. **Binary addition $1011_2 + 101_2$:** - Convert to decimal: $1011_2 = 11$, $101_2 = 5$ - Add: $11 + 5 = 16$ - Convert back to binary: $16 = 10000_2$ **Final answers:** - $B - A = \{3, 6, 9, 12, 18\}$ - $110_2 - 10_2 = 100_2$ - $1011_2 + 101_2 = 10000_2$