ANSWER:
a) 50%
b) 80%
c) It is not possible to remove all the contaminants
STEP-BY-STEP EXPLANATION:
We have the following function:
[tex]=\frac{2x}{100-x}[/tex]Where C would be the cost and x the percentage of removal, therefore:
a)
[tex]\begin{gathered} C=2 \\ \text{ replacing} \\ 2\cdot(100-x)=\frac{2x}{100-x}\cdot(100-x) \\ 2\cdot(100-x)=2x \\ 200-2x=2x \\ 4x=200 \\ x=\frac{200}{4} \\ x=50\text{\%} \end{gathered}[/tex]b)
[tex]\begin{gathered} C=8 \\ \text{ replacing} \\ 8=\frac{2x}{100-x} \\ 8\cdot(100-x)=2x \\ 800-8x=2x \\ 10x=800 \\ x=\frac{800}{10} \\ x=80\text{\%} \end{gathered}[/tex]c)
It is not possible to remove all the contaminants, due to the function nothing, since the moment that x is equal to 100, the denominator is 0, which causes a mathematical indeterminacy