1. The problem involves solving the equation derived from the proportion and percentage expressions given: $$\frac{80}{x} = \frac{100}{100} \div \frac{25}{100} = \frac{36}{x} \times \frac{100}{100}$$ 2. First, simplify the division of percentages: $$\frac{100}{100} \div \frac{25}{100} = \frac{100}{100} \times \frac{100}{25} = \frac{100 \times 100}{100 \times 25} = \frac{100}{25} = 4$$ 3. So the equation becomes: $$\frac{80}{x} = 4$$ 4. Multiply both sides by $x$ to isolate the variable: $$80 = 4x$$ 5. Divide both sides by 4 to solve for $x$: $$\cancel{\frac{80}{\cancel{4}}} = \cancel{\frac{4x}{\cancel{4}}} \Rightarrow 20 = x$$ 6. Therefore, the value of $x$ is $20$. 7. The other expressions $4(-1) - 2$ and $5 - 2(x)$ are separate and not part of the main proportion problem, so they are not solved here. Final answer: $$x = 20$$