A fruit company delivers fruit in two different size boxes: large and small. A delivery of 3

To determine the weights of the large and small boxes, we can set up a system of equations based on the information given.

Let:
- \( L \) = weight of a large box (in kg)
- \( S \) = weight of a small box (in kg)

From the information provided, we can formulate the following equations based on the weights of the boxes:

1. For 3 large boxes and 5 small boxes:
\[
3L + 5S = 135 \quad \text{(Equation 1)}
\]

2. For 9 large boxes and 7 small boxes:
\[
9L + 7S = 279 \quad \text{(Equation 2)}
\]

Now, we can solve this system of equations. We can start by multiplying Equation 1 by 3 to facilitate elimination:

\[
9L + 15S = 405 \quad \text{(Equation 3)}
\]

Now, we can subtract Equation 2 from Equation 3:

\[
(9L + 15S) - (9L + 7S) = 405 - 279
\]

This simplifies to:

\[
8S = 126
\]

Now, solve for \( S \):

\[
S = \frac{126}{8} = 15.75
\]

Now that we have \( S \), we can substitute it back into Equation 1 to find \( L \):

\[
3L + 5(15.75) = 135
\]
\[
3L + 78.75 = 135
\]
\[
3L = 135 - 78.75
\]
\[
3L = 56.25
\]
\[
L = \frac{56.25}{3} = 18.75
\]

Thus, the weights of the boxes are:
- Large box (\( L \)) = 18.75 kg
- Small box (\( S \)) = 15.75 kg

Therefore, the correct answer is:

**C. 18.75, 15.75**