Let's define the variables:

• Let $s$ be the cost of a small pizza.
• Let $m$ be the cost of a medium pizza.
• Let $l$ be the cost of a large pizza.

Based on the given information, we can set up the following equations from each package:

1. Small Gathering Package: $s + m + l = 28$

2. Family Reunion Package: $4s + 2m + l = 58$

3. Huge Party Package: $6s + 5m + 4l = 135$

We now have a system of three equations:

1. $s + m + l = 28$
2. $4s + 2m + l = 58$
3. $6s + 5m + 4l = 135$

Step 1: Eliminate $l$

Let's subtract the first equation from the second to eliminate $l$: $(4s + 2m + l) - (s + m + l) = 58 - 28$ $3s + m = 30$

This gives us a new equation: $3s + m = 30$

Step 2: Create another equation without $l$

Next, we subtract the first equation from the third: $(6s + 5m + 4l) - (s + m + l) = 135 - 28$ [ 5s + 4m + 3l = 107