To determine the gas mileage in miles per gallon (mpg), Alyssa needs to divide the number of miles she traveled by the number of gallons of gas used.

In the image, Alyssa traveled 243.8 miles and used 7.71 gallons of gas. The correct method for calculating miles per gallon is:

$\frac{243.8 \, \text{miles}}{7.71 \, \text{gallons}} = 31.62 \, \text{miles per gallon}$

So, the correct choice from the options is "243.8 miles ÷ 7.71 gallons" because dividing miles by gallons will give her the miles per gallon (mpg).

Let me know if you need more details or if you have any questions.

Here are 5 related questions to deepen your understanding:

1. How would Alyssa calculate gas mileage if she took multiple trips and refueled in between?
2. If Alyssa only traveled half the distance, what would her new mpg be with the same fuel consumption?
3. What other units could gas mileage be expressed in, such as kilometers per liter?
4. How would Alyssa calculate the total amount of fuel she would need for a long trip if she knows her mpg?
5. How does the efficiency of Alyssa’s car change if she travels uphill versus on flat ground?

Tip: Always ensure that your units match when performing calculations—especially in physics and engineering problems like this one!