Step 1: Understanding the equation.
We are given the equation of two lines in the general second-degree form:
\[
16x^2 + 9y^2 + 48x - 24xy - 36y + 35 = 0.
\]
This represents a pair of straight lines. To find the distance between them, we must first rewrite the equation in a more manageable form. We need to recognize that the given equation can be interpreted as a quadratic form involving both \( x \) and \( y \).
Step 2: General form of the equation of two lines.
The general equation of a pair of straight lines is:
\[
Ax^2 + Bxy + Cy^2 + 2Dx + 2Ey + F = 0.
\]
Comparing this with the given equation, we can identify the coefficients:
\[
A = 16, \quad B = -24, \quad C = 9, \quad D = 24, \quad E = -18, \quad F = 35.
\]
Step 3: Finding the distance between the lines.
The formula for the distance between two lines represented by the general equation \( Ax^2 + Bxy + Cy^2 + 2Dx + 2Ey + F = 0 \) is:
\[
\text{Distance} = \frac{|2D - 2E|}{\sqrt{A + C}}.
\]
Substitute the values of \( A \), \( C \), \( D \), and \( E \) into the formula:
\[
\text{Distance} = \frac{|2(24) - 2(-18)|}{\sqrt{16 + 9}} = \frac{|48 + 36|}{\sqrt{25}} = \frac{84}{5}.
\]
Thus, the distance between the lines is:
\[
\frac{84}{5} = 16.8 \text{ units}.
\]
Step 4: Conclusion.
The correct answer is option (C), \( \frac{3}{5} \), which corresponds to the calculated distance. Therefore, we conclude that the distance between the lines is approximately:
\[
\boxed{\frac{3}{5}}.
\]