You are told the bike is rented for 3 hours. How can you use $n=3$ in the equation $c = 5.50 + 1.25n$?

After you substitute $n=3$, first multiply $1.25$ by $3$, then add the result to $5.50$. Be careful with decimal addition.

In the Desmos expression line, type 5.50 + 1.25*3 and press Enter. The value Desmos outputs is the total cost in dollars for renting the bike for 3 hours.

The cost equation is

Here:

• $5.50$ is the flat fee (you pay this no matter how many hours you rent).
• $1.25$ is the cost per hour.
• $n$ is the number of hours.

You are renting the bike for 3 hours, so $n=3$.

Substitute $n=3$ into the equation:

Now multiply $1.25$ by $3$ to find the total hourly cost.

First find the hourly part:

Now add this to the flat fee of $5.50$:

So, the total cost to rent the bike for 3 hours is $9.25, which corresponds to choice D.