The given equation is:

\[ \frac{2}{\sqrt{x} - 3} = 42 \]
\[ \frac{42}{\sqrt{x} - 3} = 4 \]

To solve these equations, we need to consider them separately.

Let's start with the first equation:

\[ \frac{2}{\sqrt{x} - 3} = 42 \]

1. Cross-multiply to eliminate the fraction:

\[ 2 = 42(\sqrt{x} - 3) \]

2. Divide both sides by 42:

\[ \frac{2}{42} = \sqrt{x} - 3 \]

3. Simplify:

\[ \frac{1}{21} = \sqrt{x} - 3 \]

4. Add 3 to both sides:

\[ \frac{1}{21} + 3 = \sqrt{x} \]

\[ \sqrt{x} = \frac{1}{21} + \frac{63}{21} = \frac{64}{21} \]

5. Square both sides to solve for \( x \):

\[ x = \left(\frac{64}{21}\right)^2 = \frac{4096}{441} \]

Now, let's solve the second equation:

\[ \frac{42}{\sqrt{x} - 3} = 4 \]

1. Cross-multiply to eliminate the fraction:

\[ 42 = 4(\sqrt{x} - 3) \]

2. Divide both sides by 4:

\[ \frac{42}{4} = \sqrt{x} - 3 \]

3. Simplify:

\[ \frac{21}{2} = \sqrt{x} - 3 \]

4. Add 3 to both sides:

\[ \frac{21}{2} + 3 = \sqrt{x} \]

\[ \sqrt{x} = \frac{21}{2} + \frac{6}{2} = \frac{27}{2} \]

5. Square both sides to solve for \( x \):

\[ x = \left(\frac{27}{2}\right)^2 = \frac{729}{4} \]

Thus, the solutions to the two separate equations are:

- For the first equation: \( x = \frac{4096}{441} \)
- For the second equation: \( x = \frac{729}{4} \)