1. Olivia invested p pounds at an interest rate of y%, while Sarah invested p - 2000 pounds at an interest rate of x%.
2. Since both of them earned the same total interest, we can write this as: \(p * y\% = (p - 2000) * x\%\).
3. Let's derive p from this equation. \(p * y\% = (p - 2000) * x\% \rightarrow \frac{y\%}{x\%} = \frac{p - 2000}{p} \rightarrow \frac{y}{x} = 1 - \frac{2000}{p} \rightarrow \frac{2000}{p} = \frac{x - y}{x} \rightarrow p = \frac{2000x}{x - y}\).
4. Now let's also derive x too. \(p * y\% = (p - 2000) * x\% \rightarrow \frac{p * y\%}{p - 2000} = x\% \rightarrow x = \frac{py}{p - 2000}\).
5. Our answer will be: p - \(\frac{2000x}{x - y}\) and x - \(\frac{py}{p - 2000}\).
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There is another solution by analyzing the answer choices. The first three options are equations that don't include p but have x - that means they can only be equal to p. The other three options are equations that don't include x but have p - that means they can only be equal to x.
We can assume for each of the first three options that they equal p and try to derive x and see if the new equation is an answer choice:
- \(\frac{2000x}{x - y} = p \rightarrow px - py = 2000x \rightarrow x = \frac{py}{p - 2000}\), which is in the options.
- \(\frac{2000y}{x - y} = p \rightarrow px - py = 2000y \rightarrow x = \frac{(p + 2000)y}{p}\), which isn't in the options.
- \(\frac{200x}{x - y} = p \rightarrow px - py = 200x \rightarrow x = \frac{py}{p - 200}\), which isn't in the options.
So, our answer would be: p - \(\frac{2000x}{x - y}\) and x - \(\frac{py}{p - 2000}\).