Final answer:
Sophia can drive 459 miles using 18 gallons of gas.
Step-by-step explanation:
To find out how many miles Sophia can drive using 18 gallons of gas, we can set up a proportion based on the information given. We know that Sophia uses 8 gallons of gas to drive 204 miles, so we can set up the proportion: 8/204 = 18/x. Solve for x, the number of miles Sophia can drive:
8/204 = 18/x
Cross multiply: 8x = 204 x 18
Divide both sides by 8 to solve for x: x = (204 18)/8
Simplify: x = 459 miles
Therefore, Sophia can drive 459 miles using 18 gallons of gas.