If $S$ is the number of single-day passes, what does the 12 in $12S$ tell you? Similarly, if $W$ is the number of weekend passes, what does the 18 in $18W$ tell you?

Once you know the price of each type of pass, how can you use subtraction to find how much more one costs than the other?

In the Desmos expression line, type 18 - 12 and look at the value Desmos gives. That value is how many dollars more a weekend pass costs than a single-day pass.

The problem says the group bought $S$ single-day passes and $W$ weekend passes. That means:

• $S$ is the number of single-day passes.
• $W$ is the number of weekend passes.

So $12S$ is the total cost of all single-day passes, and $18W$ is the total cost of all weekend passes.

In an expression like $12S$, the coefficient 12 is the price per single-day pass, because $12S$ means "12 dollars times the number of single-day passes."

Similarly, in $18W$, the coefficient 18 is the price per weekend pass, because $18W$ means "18 dollars times the number of weekend passes."

So:

• Single-day pass price: $12
• Weekend pass price: $18

The question asks, "How much more does a weekend pass cost than a single-day pass?"

That means we subtract the single-day price from the weekend price:

So, a weekend pass costs $6 more than a single-day pass.