If gas is $3.29 and the car gets 20 miles per gallon, how do you figure how much money will be spent on gas..?

We have insufficient information. We need the speed.

Let speed = v

Distance = 9v miles

Gallons = 9v/20 gallons

Cost = $(9v/20) * 3.29

Yeah it has to do with miles and not hours driven.

I'll assume you're going about 70 mph or so, and going to take a few stops for food/gas. So about 650 miles?

So you'd do $3.29 (dollars/gallon) x 650 miles / 20 (miles/gallon)

If you do the math, you'll notice that both 'miles' terms cancel out because of the fraction, and the 'gallon' terms cancel out, so your answer will be in dollars (it's a way of making sure you set everything up correctly!)

So that gives you 2138.5/20, or $107. Note that if you're going there and back it will be double.

And I'm kinda jealous you have $3.29 gas....

You are making it impossible since the gas price changes by location and you are not stating how many miles your trip is.

Rather you supply the amount of miles to travel rather than the time of driving.

the consume of gas also depends on the speed of the car and the time that you change the speed (aceleration and brake)