1. The problem is to evaluate the expression $$\frac{a - b}{\frac{1}{2}}$$ for given values of $a$ and $b$. 2. The formula used is division of a difference by a fraction: $$\frac{a - b}{\frac{1}{2}} = (a - b) \times 2$$ This is because dividing by $\frac{1}{2}$ is equivalent to multiplying by 2. 3. Let's verify the first expression: $$\frac{1 - 2}{\frac{1}{2}}$$ Calculate numerator: $$1 - 2 = -1$$ Then divide by $\frac{1}{2}$: $$\frac{-1}{\frac{1}{2}} = -1 \times 2 = -2$$ The given answer is $-7$, which does not match the calculation, so there might be a typo or different interpretation. 4. Let's check the second expression: $$\frac{4 - 4}{\frac{1}{2}}$$ Calculate numerator: $$4 - 4 = 0$$ Divide by $\frac{1}{2}$: $$\frac{0}{\frac{1}{2}} = 0 \times 2 = 0$$ Given answer is $-12$, which again does not match. 5. Third expression: $$\frac{3 - 1}{\frac{1}{2}}$$ Calculate numerator: $$3 - 1 = 2$$ Divide by $\frac{1}{2}$: $$\frac{2}{\frac{1}{2}} = 2 \times 2 = 4$$ Given answer is $8$, which is double our result. 6. Fourth expression: $$\frac{4 - 1}{\frac{1}{2}}$$ Calculate numerator: $$4 - 1 = 3$$ Divide by $\frac{1}{2}$: $$\frac{3}{\frac{1}{2}} = 3 \times 2 = 6$$ Given answer is $12$, again double. 7. Fifth expression: $$\frac{4 - 0}{\frac{1}{2}}$$ Calculate numerator: $$4 - 0 = 4$$ Divide by $\frac{1}{2}$: $$\frac{4}{\frac{1}{2}} = 4 \times 2 = 8$$ Given answer is $16$, double again. 8. It appears the given answers are twice the expected values from the formula. Possibly the denominator is $\frac{1}{4}$ instead of $\frac{1}{2}$ or the multiplication factor is 4. 9. If we consider denominator as $\frac{1}{4}$, then: $$\frac{a - b}{\frac{1}{4}} = (a - b) \times 4$$ Check first expression: $$1 - 2 = -1$$ $$-1 \times 4 = -4$$ Still not $-7$. 10. Alternatively, the given answers might be from a different context or contain errors. Final answer for the first expression using the formula is: $$\frac{1 - 2}{\frac{1}{2}} = -2$$