May I ask what’s this answer?
I wasn’t in class today:(

Explanation:

For every 5 gallons, there's 120 miles. If we know we have 360 miles, we can see how many times 120 goes into 360, which is 3.

5 * 3 = 15.

Then just reverse the process

it's equivalent, so we can say that its equal.

let's call the denominator x and the numerador is 18 less then denominator, x - 18.

multiply

2.x = 5.(x - 18)

2x = 5x - 90

90 = 5x - 2x

90 = 3x

x = 90/3

x = 30

so: