Let's denote the salaries of A, B, and C as \( S_A \), \( S_B \), and \( S_C \) respectively. We are given that:

\[ S_A + S_B + S_C = 3000 \]

We are also given that A spends 95% of their salary, B spends 85% of their salary, and C spends 80% of their salary. This means that A saves 5% of their salary, B saves 15% of their salary, and C saves 20% of their salary. 

So, the savings of A, B, and C can be represented as:

\[ \text{Savings}_A = 0.05S_A \]
\[ \text{Savings}_B = 0.15S_B \]
\[ \text{Savings}_C = 0.20S_C \]

We are told that the sum of A's and B's savings is equal to C's savings:

\[ \text{Savings}_A + \text{Savings}_B = \text{Savings}_C \]
\[ 0.05S_A + 0.15S_B = 0.20S_C \]

And B's savings are twice A's savings:

\[ \text{Savings}_B = 2 \times \text{Savings}_A \]
\[ 0.15S_B = 2 \times 0.05S_A \]
\[ 0.15S_B = 0.10S_A \]

Now we have three equations:

1. \( S_A + S_B + S_C = 3000 \)
2. \( 0.05S_A + 0.15S_B = 0.20S_C \)
3. \( 0.15S_B = 0.10S_A \)

From equation 3, we can express \( S_A \) in terms of \( S_B \):

\[ S_A = \frac{0.15}{0.10}S_B \]
\[ S_A = 1.5S_B \]

Now we can substitute \( S_A \) in equation 1 with \( 1.5S_B \):

\[ 1.5S_B + S_B + S_C = 3000 \]
\[ 2.5S_B + S_C = 3000 \]

And we can substitute \( S_A \) in equation 2 with \( 1.5S_B \):

\[ 0.05(1.5S_B) + 0.15S_B = 0.20S_C \]
\[ 0.075S_B + 0.15S_B = 0.20S_C \]
\[ 0.225S_B = 0.20S_C \]

Now we can express \( S_C \) in terms of \( S_B \):

\[ S_C = \frac{0.225}{0.20}S_B \]
\[ S_C = 1.125S_B \]

Substitute \( S_C \) in the equation \( 2.5S_B + S_C = 3000 \) with \( 1.125S_B \):

\[ 2.5S_B + 1.125S_B = 3000 \]
\[ 3.625S_B = 3000 \]
\[ S_B = \frac{3000}{3.625} \]
\[ S_B = 827.59 \]

Now we can find \( S_A \) and \( S_C \):

\[ S_A = 1.5S_B \]
\[ S_A = 1.5 \times 827.59 \]
\[ S_A = 1241.39 \]

\[ S_C = 1.125S_B \]
\[ S_C = 1.125 \times 827.59 \]
\[ S_C = 930.79 \]

So the salaries of A, B, and C are approximately $1241.39, $827.59, and $930.79 respectively.
A, B, C의 급여를 각각 \( S_A \), \( S_B \), \( S_C \)로 표시해 보겠습니다. 다음과 같이 주어집니다:

\[ S_A + S_B + S_C = 3000 \]

또한 A는 급여의 95%를, B는 급여의 85%를, C는 급여의 80%를 지출한다고 가정합니다. 즉, A는 급여의 5%, B는 급여의 15%, C는 급여의 20%를 저축합니다.

따라서 A, B, C의 저축액은 다음과 같이 표현할 수 있습니다:

\[ \text{저축액}_A = 0.05S_A \]
\[ \text{저축액}_B = 0.15S_B \]
\[ \text{저축액}_C = 0.20S_C \]

A와 B의 저축액의 합은 C의 저축액과 같다고 합니다:

\[ \text{저축액}_A + \text{저축액}_B = \text{저축액}_C \]
\[ 0.05S_A + 0.15S_B = 0.20S_C \]

그리고 B의 저축액은 A의 저축액의 두 배입니다:

\[ \text{저축액}_B = 2 \times \text{저축액}_A \]
\[ 0.15S_B = 2 \times 0.05S_A \]
\[ 0.15S_B = 0.10S_A \]

이제 세 개의 방정식이 생겼습니다:

1. \( S_A + S_B + S_C = 3000 \)
2. \( 0.05S_A + 0.15S_B = 0.20S_C \)
3. \( 0.15S_B = 0.10S_A \)

방정식 3을 통해 \( S_A \)를 \( S_B \)로 표현할 수 있습니다:

\[ S_A = \frac{0.15}{0.10}S_B \]
\[ S_A = 1.5S_B \]

이제 방정식 1에서 \( S_A \)를 $1.5S_B$로 대입할 수 있습니다:

\[ 1.5S_B + S_B + S_C = 3000 \]
\[ 2.5S_B + S_C = 3000 \]

그리고 방정식 2에서 \( S_A \)를 $1.5S_B$로 대입할 수 있습니다:

\[ 0.05(1.5S_B) + 0.15S_B = 0.20S_C \]
\[ 0.075S_B + 0.15S_B = 0.20S_C \]
\[ 0.225S_B = 0.20S_C \]

이제 \( S_C \)를 \( S_B \)로 표현할 수 있습니다:

\[ S_C = \frac{0.225}{0.20}S_B \]
\[ S_C = 1.125S_B \]

방정식 \( 2.5S_B + S_C = 3000 \)에서 \( S_C \)를 $1.125S_B$로 대입합니다:

\[ 2.5S_B + 1.125S_B = 3000 \]
\[ 3.625S_B = 3000 \]
\[ S_B = \frac{3000}{3.625} \]
\[ S_B = 827.59 \]

이제 \( S_A \)와 \( S_C \)를 구할 수 있습니다:

\[ S_A = 1.5S_B \]
\[ S_A = 1.5 \times 827.59 \]
\[ S_A = 1241.39 \]

\[ S_C = 1.125S_B \]
\[ S_C = 1.125 \times 827.59 \]
\[ S_C = 930.79 \]

따라서 A, B, C의 급여는 각각 약 $1241.39, $827.59, $930.79입니다.