gas question

So im completly retarted when it comes to doing math. So I figured Id post to hopefully get a little help regarding tank size and gallons per. So I know tacomas have a 21 gallon tank, and some of that is actually part of the reserve...So im really trying to figure out how many gallons are in the actual tank and how many gallons each quarter would approx. equal out to.....Hope this makes sense! (Note-3/4 to fill the tank is equal to ____ gallons of fuel. which in turn at $3.30 a gallon would equal to $______ to fill the tank.)


Thanks! Also, sorry if I put this in the wrong forum

 

1 * 21 / 4 * 3.30 = $17.325 per quarter tank

 

Awesome thanks!!! That makes way more sense than what I was doing.....haha