The total payment $p$ includes the activation fee $a$ and the total monthly cost you just found. How can you write $p$ in terms of $a$ and that number?

Once you have an equation like $p =$ (something), try adding or subtracting the same quantity from both sides so it looks like one of the choices.

In Desmos, type the equation that directly matches the situation: p = a + 24 (total payment equals activation fee plus $24$ dollars from the 8 months). This is your “story equation.”

For each answer choice, solve it for $p$ on paper (get $p =$ ...), then type that new form into Desmos as a separate equation. Compare the graphs: the choice whose graph exactly overlaps the graph of p = a + 24 for all values of $a$ is the one that represents the same relationship.

The subscription costs $3$ dollars per month.

For 8 months, the total monthly charge is:

$3 \times 8 = 24$ dollars.

So, across 8 months, the customer pays $24$ dollars just for the monthly fee.

The total payment $p$ is made up of:

• the one-time activation fee: $a$ dollars
• the total monthly charges: $24$ dollars

So we can write the relationship as:

$p = a + 24$

This equation directly models the story.

The answer choices don't show $p = a + 24$ exactly, so rearrange it.

Subtract $a$ from both sides of $p = a + 24$:

$p - a = 24$

This matches choice B, so the correct equation is $p - a = 24$.